Liver and intrahepatic bile ducts - Nontumor

Right lobe is divided into anterior and posterior segments by right hepatic vein; left lobe is divided into medial and lateral segments by left hepatic vein

Intrahepatic biliary tree: classified into intrahepatic large bile ducts (grossly visible with fibrous ductal wall and peribiliary glands) and small bile ducts

Regional lymph nodes: hilar, hepatoduodenal ligament, caval

Normal histology

Size of structures varies according to closeness to hepatic hilum

Acini

Hemodynamic model of hepatic microanatomy that explains centrilobular necrosis; a concept, not an identifiable microscopic structure; triangular (spherical) area; base is terminal twigs of hepatic artery and portal vein

Bile canaliculi

Drain bile from hepatocytes to portal space; 1-2 micron wide areas between neighboring hepatocytes, formed by grooves in plasma membranes and separated from vascular space by tight junctions; intracellular actin and myosin filaments surrounding the canaliculi propel secreted biliary fluid along canaliculi into canals of Hering, the terminal tributaries of the bile duct system (low cuboidal epithelium), to interlobular bile ducts (more robust cuboidal epithelium); connected to bile ducts by cholangioles (bile ductules), usually not visible unless distended by bile; highlighted by CEA which stains biliary glycoprotein I in canalicular membrane (cross reacting substance)

Bile ducts (intrahepatic)

Develop from primitive hepatocytes of periportal limiting plate

Micro: cuboidal cells with mildly basophilic cytoplasm and single nuclei

Positive stains: CK7, CK 8/18, CK 19

Bile ductules

Also called ductular cells, cholangioles

Converge from hepatic lobule onto portal tract and connect bile canaliculi to the interlobular bile ducts

Represent the most proximal portion of the bile drainage pathway with a cholangiocyte lining

Usually not seen in normal liver

Proliferate in pathologic conditions, and can differentiate into hepatocytes to repopulate a destroyed liver

Micro: small ovoid cells lying singly at periphery of portal tract or as strings within the lobule; not accompanied by artery

Positive stains: CK7, CK8, CK18, CK19, HLA-DR

Central veins

Also called terminal hepatic venules (NOT terminal hepatic vein); smallest component of venous outflow tract, merge to form hepatic veins, then empty into inferior vena cava

Hepatocytes

Polygonal cells 25-30 microns, arranged in three dimensional plates that radiate away from central vein towards portal tracts; one cell thick at age 5 years or more, two cells thick in children ages 0-5 years; are lined by sinusoids on two sides in which blood flows from portal space to central vein; also have biliary and lateral surfaces (for attachment to adjacent hepatocytes); cells are uniform with abundant granular and eosinophilic cytoplasm with scattered fat vacuoles, glycogen and lipofuscin (prominent in centrilobular hepatocytes, increases with age); have central round to oval nuclei, but nuclei may be pleomorphic and multiple (all mononuclear at birth, 10% binuclear at 8 years, 15% at 15 years, 25% in adults); hepatocytes are continuously renewed with proliferation near portal space and death near central vein at 50-300 days; mitotic figures are rare

Kupffer cells

Attached to endothelium in space of Disse

Phagocytic cells that are part of reticuloendothelial system; triangular or star shaped with bean-shaped nuclei and clear to granular cytoplasm

Proliferate and enlarge in response to hepatocyte damage

Degrade hemoglobin to unconjugated bilirubin

Contain ceroid pigment, PAS+ diastase resistant granules that represent degraded cellular debris

Positive stains: macrophage markers (lysozyme, CD68)

Limiting plate

Encircling ring around portal tracts formed by lamina propria of hepatocytes immediately abutting the portal tract; disrupted by inflammation with hepatocellular death (piecemeal necrosis)

Lobules

Traditional model of hepatic microanatomy; 1-2 mm hexagonal area with a central terminal hepatic venule (also called central vein) and 3-6 portal tracts at periphery; centrilobular zone surrounds central vein and periportal zone adjoins portal tract; zone 1 is closest to vascular supply/portal tract, zone 3 is closest to central vein, is called centrilobular area, is furthest from arterial blood and most prone to vascular insults

Portal triad / portal tract

Contains intrahepatic bile ducts, branches of hepatic artery and branches of portal vein; 70-80% of arteries are normally accompanied by bile ducts; normally contains small numbers of lymphocytes and macrophages and occasional mast cells and eosinophils; no neutrophils or plasma cells normally; row of hepatocytes around portal tract is ductal plate (limiting plate), contains stem cells responsible for bile duct growth and development; bile ducts are lined by cuboidal epithelium; portal tracts are more fibrotic in subcapsular zone

Reticulum

Collagen fibers in space of Disse, stain black with silver impregnation, produced by Ito cells; forms supporting framework of hepatocytes; if present, even necrotic liver can regenerate; if damaged, liver heals with fibrosis and possibly cirrhosis

Sinusoids

Interposed between hepatic plates, carry arterial/venous blood to terminal hepatic vein, lined by fenestrated and discontinuous endothelial cells and Kupffer cells, which demarcate an extrasinusoidal space of Disse into which hepatocyte microvilli protrude; endothelial cells lack a basement membrane and the endothelial markers of larger vessels

Negative stains: von Willebrand Factor, CD34, Ulex europaeus

Stellate cells

Also called Ito cells

Fat-containing hepatic stellate cells of mesenchymal origin in space of Disse

Not normally seen on routine H&E sections

Activated after injury and transformed into myofibroblasts with liver fibrosis and inflammation

Store and metabolize Vitamin A; may become laden with fat in hypervitaminosis A

Positive stains: smooth muscle actin, desmin

Embryology

Hepatic diverticulum buds from ventral foregut at end of third week, grows into primitive septum transversum

Liver forms from endodermal cells of diverticulum and mesenchyme

Blood supply primarily from umbilical vein; also portal vein and hepatic artery

Placenta clears wastes in bile and absorbs nutrients, and umbilical vein blood bypasses liver via ductus venosus

Bile duct system not complete until after birth; derived from endoderm (large ducts) and embryonic ductal plate (smaller intrahepatic ducts)

Hematopoietic cells are present in embryonic/fetal liver but absent at term

Normal physiology

Bile: promotes dietary fat absorption via detergent action of bile salts; eliminates waste products (bilirubin, excess cholesterol, xenobiotics that are insufficiently water soluble to be excreted into urine)

Bile acids: carboxylate steroid molecules, derived from cholesterol, that promote bile flow and secretion of phospholipid and cholesterol; primary bile acids are cholic acid and chenodeoxycholic acid, secreted as tuarine and glycine conjugates

Bile acid circulation: all bile acids are reabsorbed via sodium-bile acid cotransporter in apical membrane of ileal enterocytes, and transported back to liver; enterohepatic circulation of bile acids maintains a large endogenous pool of bile acids for digestive and excretory purposes

Jaundice: also called icterus; discoloration of skin and sclera due to disruption of bile formation by either retention of pigmented bilirubin or block in bilirubin secretion (cholestasis)

Bilirubin: end product of heme degradation; 200 mg produced daily from old red blood cells broken down via monocyte phagocytic system in spleen, liver, marrow; also from turnover of P450 cytochromes and premature destruction of marrow red blood cells (with ineffective erthyropoiesis)

Red blood cells are broken down and produce hemoglobin

Globin proteins are removed, leaving heme molecule

Heme is converted to biliverdin via heme oxygenase

Biliverdin is converted to bilirubin via biliverdin reductase

Bilirubin is bound to serum albumin since it is insoluble in blood at physiologic pH; the % unbound increases in severe hemolytic disease or if protein-binding drugs displace bilirubin

Hepatocytes take in bilirubin at sinusoidal membrane, conjugate it with glucuronic acid using bilirubin uridine diphosphate-glucuronosyltransferase (UGT) in endoplasmic reticulum, then bilirubin is excreted into bile

Bacteria have beta glucuronidases which deconjugate and degrade bilirubin to colorless urobilinogens, excreted in feces

20% of urobilinogens are reabsorbed in ileum/colon, returned to liver, re-excreted into bile

Patterns of hepatic injury

Acidophil body: type of focal necrosis in which dead hepatocyte is identifiable as shrunken, eosinophilic round body with variable nucleus, usually not accompanied by inflammation; also called Councilman body, single cell death, apoptotic cell; signifies nonspecific hepatocellular injury

Ballooning (feathery) degeneration: swelling of hepatocytes with increased and pale cytoplasm, nonspecific; leads to lytic necrosis and replacement by inflammatory cells

Bile ductules (see also above): proliferate in pathologic conditions, and can differentiate into hepatocytes to repopulate a destroyed liver

Bridging necrosis: necrotic cells spans adjacent lobules in portal-portal, portal-central or central-central pattern

Centrilobular necrosis: necrotic hepatocytes around terminal hepatic venule, usually due to ischemia, drugs or toxins; common finding at autopsy, because it is associated with circulatory failure or shock which is common before all deaths

Giant cell transformation: hepatocyte with 6 or more nuclei

Glycogen nuclei: homogenous clearing of hepatocyte nuclei, usually with enlargement, usually periportal; seen in most biopsies in a few nuclei; abundant in hyperglycemia, glycogen storage disease, Wilson’s disease, nonalcoholic steatohepatitis

Ground glass cells: eosinophilic granular cytoplasm, due to drug reaction (proliferation of endoplasmic reticulum diffusely throughout cell), oncocytic change (proliferation of mitochondria), hepatitis B infection (granules are surface antigen, focal)

Interface hepatitis: inflammatory cells between inflamed portal tracts and periportal parenchyma

Interlobular bile duct: bile duct of medium sized portal tract that is centrally located in tract and accompanies similarly sized arteriole

Large cell change: also called large cell dysplasia; atypical hepatocytes with nuclear and cytoplasmic enlargement, nuclear pleomorphism with hyperchromasia, multinucleation but normal nuclear to cytoplasmic ratio; often periseptal; don’t deform surrounding architecture; may be associated with prolonged cholestasis; appears to NOT be a premalignant condition

Mallory’s hyaline: also called Mallory bodies; irregular, rope-like, sharply defined, intracytoplasmic eosinophilic deposits of cytokeratin, may assume C-shape around nucleus, often in ballooning cells, surrounded by neutrophils in alcoholic liver disease; associated with alcoholic and nonalcoholic steatohepatitis, various cholestatic conditions, Wilson’s disease

Microvesicular steatosis: multiple tiny intracytoplasmic fat droplets that do not displace the nucleus; may be so small that they simulate ballooning degeneration; associated with alcoholic liver disease, acute fatty liver of pregnancy, outdated tetracycline, valproic acid, Reye’s syndrome, nucleoside analog therapy for HIV (Archives 1999;123:189)

Macrovesicular steatosis: single large intracytoplasmic fat droplet that displaces nucleus; associated with alcoholic liver disease, obesity, diabetes, nonalcoholic steatohepatitis, drug reactions, cystic fibrosis

Necrosis: may be bridging (joins structures such as portal tracts), confluent (clusters of adjacent hepatocytes), focal (individual hepatocytes, usually apoptosis), massive (all hepatocytes in biopsy), piecemeal (below) or zonal (specific region such as centrilobular)

Necrosis, piecemeal: necrosis of hepatocytes at limiting plate; either necrosis of cells or irregularity of limiting plate caused by loss of hepatocytes and replacement with inflammatory cells or fibrosis; usually minimal lobular inflammation is present

Passive congestion: common finding at autopsy, because associated with circulatory failure which is common before all deaths; also called nutmeg liver; due to right sided cardiac decompensation; liver large, tense, cyanotic around edges with congestion of centrilobular sinusoids; over time, get centrilobular necrosis

Small cell change: also called small cell dysplasia; small hepatocytes with increased nuclear density; may have basophilic cytoplasm, but no significant nuclear atypia or enlargement; usually present in clusters; found in regeneration, atrophy, premalignant or malignant conditions

Submassive necrosis: prominent necrosis involving centrilobular zones or entire lobules in most of liver: associated with hepatic failure; bile ductular proliferation prominent in necrotic zones in late stages; no significant collagen or elastic fiber deposition; collapse of reticulin network in necrotic zones

Biopsy

Core biopsies are 1-3 cm by 1-2 mm, representing only .002% of total liver mass

Adequacy important; difficult to diagnosis chronic hepatitis with less than 4 identifiable portal tracts

Recommended to routinely obtain levels, trichrome stain (highlights type I collagen), possibly reticulin stain (highlights type III collagen framework) and iron stain (to assess iron overload)

“Clinical history is necessary to render an interpretation rather than a description of the biopsy” - Rosai

Difficult to differentiate well differentiated hepatocellular carcinoma from benign lesions, or poorly differentiated hepatocellular carcinoma as hepatic origin on small biopsy

Features to examine: adequate of biopsy, site of biopsy (is it from liver?), architecture on low power; portal tracts, lobules, central veins; assess inflammation (degree, type), necrosis, fibrosis, tumor cells

portal tracts: presence of vein, artery and bile duct

inflammation: type, severity, relationship to bile duct or other structures

bile duct changes: inflammation, proliferation or loss, necrosis, cholestasis, atypia

vascular changes: inflammation, thrombosis, thickening

lobular changes: inflammation, necrosis, sinusoids, cell plates, inclusions, amyloid, fibrosis

central veins: size and shape, inflammation and fibrosis

Final diagnosis should include clinical data, as histologic features are usually insufficient for a nonneoplastic diagnosis

Diagnostic patterns-differential diagnosis

Adopted from Sternberg, S: Diagnostic Surgical Pathology (3rd Ed); Lippincott Williams & Wilkins, 1999

Lobular lymphocytic infiltrate: acute viral hepatitis (A, B, C, delta virus, CMV, EBV), autoimmune hepatitis, extramedullary hematopoiesis (not actually lymphocytes), leukemia, lymphoma, mastocytosis, primary biliary cirrhosis

Lobular neutrophilic infiltrate: alcoholic hepatitis, post-surgical, viral hepatitis, sepsis

Portal lymphoplasmacytic infiltrate with minimal lobular inflammation or degeneration/necrosis: resolving acute hepatitis, autoimmune hepatitis, chronic bile duct obstruction, graft versus host disease, leukemia/lymphoma, area adjacent to granuloma or neoplasm, primary biliary cirrhosis, primary sclerosing cholangitis, graft rejection, hepatitis B or C, Wilson’s disease, steatohepatitis

Variable involvement of portal tracts suggests primary biliary cirrhosis, hepatitis C, steatohepatitis; extensive piecemeal necrosis suggests autoimmune hepatitis; lack of eosinophils or plasma cells makes hepatitis C or Wilson’s disease less likely; exclusive lymphocytic infiltrate favors hepatitis C; bile duct loss and bile ductular proliferation favor primary biliary cirrhosis or primary sclerosing cholangitis; granulomas favor primary biliary cirrhosis

Portal neutrophilic infiltrate with minimal lobular inflammation or degeneration/necrosis: ascending cholangitis, acute biliary tract obstruction, hyperalimentation, medication reaction, viral hepatitis

Portal eosinophilic infiltrate: autoimmune hepatitis, extramedullary hematopoiesis, drug reaction, parasites, primary biliary cirrhosis, primary sclerosing cholangitis, rejection

Hepatocellular necrosis with minimal inflammation: ischemia, fulminant hepatitis, drug/toxin reaction, trauma, acute hepatitis in immunocompromised, hepatic venous outflow obstruction, epithelioid hemangioendothelioma

Congestion/hemorrhage: venous outflow disease, Budd-Chiari syndrome, congestive heart failure, angiosarcoma or epithelioid hemangioendothelioma, nodular regenerative hyperplasia, peliosis hepatis

Pigments: bile (green-brown, usually in bile ducts or bile canaliculi, usually centrilobular), iron (gold-brown, usually periportal but centrilobular with congestive liver disease, in hepatocytes in primary hemochromatosis, in Kupffer cells secondary to hemolysis, iron overload or hepatocyte necrosis; highlighted with Prussian blue stain), lipofuscin (brown, in centrilobular hepatocytes, highlighted with Fite stain), gold (brown-black in Kupffer cells in arthritis patients), thorium dioxide / Thorotrast (gray-blue in Kupffer cells)

Inclusions: adenovirus, alpha-1-antichymotrypsin, alpha-1-antitrypsin deficiency, amylopectin, CMV, glycogen nuclei, herpes, Mallory’s hyaline, macrovesicular steatosis, microvesicular steatosis

Fatty change with no/mild necrosis: alcoholic steatohepatitis, fatty liver of pregnancy, biopsy associated, hepatocellular adenoma or carcinoma, drug/toxin reaction, metabolic disease (features defined by specific disease), nonalcoholic steatohepatitis, nonspecific, Wilson’s disease

Nearly normal biopsy: hepatoportal sclerosis, drug/toxin reaction, missed lesion, nodular regenerative hyperplasia, metabolic diseases

Loss of bile ducts: mild to moderate if less than 0.9 bile ducts per portal tract; severe if less than 0.6 bile ducts per portal tract; causes include chronic biliary tract obstruction, primary biliary cirrhosis, primary sclerosing cholangitis, paucity in neonates, idiopathic adult ductopenia, drug reaction (Augmentin), ischemia, chronic graft versus host disease, chronic graft rejection

Loss of central veins: sampling error, cirrhosis, hepatocellular adenoma or carcinoma, nodular regenerative hyperplasia (central veins present but difficult to see)

Loss of hepatocytes: massive hepatic necrosis / fulminant hepatitis

Loss of portal tracts: sampling error, cirrhosis, hepatocellular adenoma or carcinoma

Loss of portal veins but portal tracts present: hepatoportal sclerosis

Loss of sinusoids: metabolic storage diseases, cirrhosis

Developmental anomalies/cysts

Accessory lobe

May appear clinically as hepatic mass

Alagille’s syndrome

Also called arteriohepatic dysplasia

Autosomal dominant, due to mutations in Jagged1 gene on #20p, which encodes a ligand for Notch1 and plays a role in epithelial-mesenchymal interactions

Normal liver, but no portal tract bile ducts (progressive loss, may occasionally regrow)

Characteristic facies, vertebral arch anomalies, supravalvular pulmonic stenosis

May survive into adulthood, but increased risk of hepatic failure and hepatocellular carcinoma

Bloom syndrome

Rare, autosomal recessive, with normally proportioned but markedly small body size, characteristic facies, photosensitive facial skin lesion, immunodeficiency, marked predisposition to variety of cancers.

Case report of pronounced sclerosing hyaline necrosis of liver with Mallory bodies, Archives 1999;123:346

Byler’s disease

Impaired secretion of bile salts and phosphatidylcholine causes progressive intrahepatic cholestasis

Micro: enlarged portal tracts with inflammation, ductular proliferation and fibrosis

Caroli’s disease

Also called communicating cavernous biliary ectasia

Autosomal recessive disorder, mildly associated with autosomal dominant and autosomal recessive polycystic kidney disease

Due to arrest of remodeling of ductal plate of larger intrahepatic bile ducts

Larger ducts of intrahepatic biliary tree are segmentally dilated and may contain inspissated bile

Usually associated with congenital hepatic fibrosis; often associated with intrahepatic cholelithiasis, cholangitis, liver abscess and portal hypertension

7-14% develop dysplasia and cholangiocarcinoma

Often gallstones, ulcer, hyperplasia

Poor prognosis, with death due to sepsis or liver failure

Caroli’s syndrome: Caroli’s disease plus congenital hepatic fibrosis

Gross: 1-4 cm cysts separated by normal bile ducts

Micro: dilated ducts lined by cuboidal or columnar epithelium with fibrotic duct wall

DD: primary sclerosing cholangitis

Choledochal cyst

Classically presents with pain, right upper quadrant mass and jaundice, particularly in children

Cholangitis symptoms may predominate in adults

Usually women

14% develop adenocarcinoma with increasing age

Gross: often huge cysts

Micro: thick fibrous wall, often inflamed; discontinuous columnar epithelium; variable squamous metaplasia

Congenital hepatic fibrosis

Progressive lesion associated with autosomal recessive infantile polycystic kidney disease, mildly associated with autosomal dominant polycystic kidney disease

Often diagnosed in adolescents with portal hypertension

May be due to ductal plate malformation of intralobular bile ducts

Complications: portal hypertension, cholangitis

Gross: entire liver affected by microscopic cysts; rarely macroscopic hepatic cysts

Micro: anastomosing biliary channels in irregular, bland fibrous stroma, continuous with biliary tree, hepatocyte nodules with central veins and normal architecture; marked proliferation of bile ductules; angulated bile ducts often with inspissated bile in fibrotic portal tracts with portal-portal bridging fibrosis; no inflammation, no regenerative nodules

Down’s syndrome

Case report associated with liver fibrosis, thought due to megakaryocyte derived transforming growth factor beta, Hum Path 1999;30:474

Extrahepatic biliary atresia

Most common cause of pathologic infant jaundice; common reason for pediatric liver transplantation

Definition: total or partial loss of permeable bile ducts between porta hepatis and duodenum

Typically presents with symptoms at 1-2 months of age

Stenotic or atretic portions of extrahepatic biliary tree cause chronic extrahepatic large duct obstruction

May have infectious or autoimmune etiology

Histologically resembles choledochal cyst or other causes of large duct obstruction

Note: since biopsies have 7% false-positive rate, radiographic studies are mandatory

Treatment: hepatoportenterotomy (Kasai procedure), liver transplant; to assess likelihood of success of surgical correction, surgeon may biopsy porta hepatis, pathologist indicates size and number of bile ducts present; also indicates amount of fibrosis and inflammation

Micro: lobular cholestasis, portal neutrophilic infiltrate, bile ductular proliferation (peaks at 200 days), with elongated and angulated ductules and occasional bile plugs; variable vacuoles and lymphocytes; late-fibrosis or cirrhosis; may have focal giant cell transformation (periportal, not extensive), ductopenia (occurs rapidly at 400 days) and focal extramedullary hematopoiesis

Positive stains: CD56 (biliary epithelium stains strongly in >65% of portal tracts)

Molecular: 10% have mutations in Jagged 1 gene (associated with Alagille’s syndrome)

References: AJSP 2003;27:1454 (CD56)

DD: alpha-1-antitrypsin deficiency, congenital cytomegalovirus infection, neonatal hepatitis

Foregut cyst

Rare, < 100 cases reported

Intrahepatic ileal and duodenal duplications and ciliated foregut cysts have been described

4 cm or smaller, have smooth muscle bundles in cyst wall

Slightly more common in men, and in medial segment of left hepatic lobe

Resemble bronchiolar epithelium

Case reports: ciliated foregut cyst with squamous cell carcinoma, Archives 1999;123:1115

Gross: solitary, rarely multilocular, 1-4 cm

Micro: ciliated pseudostratified columnar epithelium with goblet cells, subepithelial connective tissue, 1-3 smooth muscle layers, outer fibrous capsule

References: AJSP 1999;23:671, Hum Path 2000;31:241

Intrahepatic biliary atresia

Also called paucity of intrahepatic bile ducts in neonates

Occurs in syndromic form (Alagille’s syndrome) or nonsyndromic form

In nonsyndromic form, bile duct loss is present from birth; may actually represent cystic fibrosis, alpha-1-antitrypsin deficiency, trihydroxycoprostanic acidemia; bile duct recovery depends on etiology

Micro: loss of interlobular bile ducts (0.5 ducts/portal tract vs. normal 0.9-1.8 ducts/portal tract; count only bile ducts accompanying hepatic arterioles in center of portal tracts, keratin staining may be helpful); usually minimal ductular proliferation; no/minimal fibrosis, no/minimal inflammation

Multiple hilar cysts

Arise from peribiliary glands surrounding extrahepatic and large intrahepatic bile ducts in hilum

Cysts are incidental finding in 20% of autopsies

May compress adjacent bile duct; also associated with cirrhosis and portal vein thrombosis

Gross: up to 2 cm, unilocular with clear serous fluid, if multiple may make liver appear spongy

Micro: lined by columnar to cuboidal epithelium with mild chronic inflammatory infiltrate, fibrosis, fibrous obliteration of small veins; occasional hyperplasia

Polycystic liver disease

Autosomal dominant, associated with autosomal dominant (but not autosomal recessive) polycystic kidney disease (71-93%) and defect in ADPKD1 gene on #16

Cysts don’t communication with biliary tree

80% occur in females

Associated with abdominal tenderness, pain with stooping; may present during pregnancy

Cysts more common with increased age (75% at age 70+ vs. <5% in teenagers)

1-7% risk of adenocarcinoma if coexisting Caroli’s disease; otherwise extremely rare

Complications: infection, cholangiocarcinoma, squamous cell carcinoma

Gross: multiple variably sized unilocular cysts, liver rarely is massively enlarged

Micro: multiple diffuse cystic lesions resembling solitary cysts, lined by cuboidal to flat biliary epithelium, containing straw colored fluid; 40% have identifiable von Meyenburg complexes; don’t contain pigmented material

Solitary cyst

Also called unilocular, simple or congenital cyst

Not associated with cysts in other organs

80% occur in women

Usually incidental finding; may be due to von Meyenburg complexes that separate from biliary tree and dilate

20x more common than cystadenomas; present in 14% of autopsies if looked for

Complications are torsion, hemorrhage, rupture, compression of adjacent biliary tree; rarely carcinoma arises in these cysts

Treatment: excision, sclerotherapy, cyst fenestration

Gross: single, unilocular cyst, usually subcapsular or in falciform ligament; 2-40 cm with flat glistening lining; variable amounts of clear amber fluid (may contain blood, bile, mucus, pus); usually separate from biliary tree

Micro: lined by biliary-type epithelium (flat/cuboidal), occasionally ciliated (called foregut cyst) or squamous lined (epidermoid cyst); epithelium rests on thin collagenous wall without spindle-cell stroma

Degenerative changes include epithelial desquamation, multiloculation, calcification

von Meyenburg complex

Also called bile duct hamartoma or microhamartoma

Incidental finding in 6% of adults and 1% of children at autopsy; found in 1% of all liver needle biopsies

No clinical significance, although may resemble liver metastases to surgeons

Associated with autosomal dominant polycystic hepatorenal disease, other ductal plate malformations such as congenital hepatic fibrosis and Caroli’s disease

Due to incomplete involution of embryonic bile duct remnants; a type of ductal plate malformation

Rarely associated with neoplastic transformation to hyperplasia, adenoma and cholangiocarcinoma, AJSP 2000;24:1131, Archives 2000;124:1704

Gross: single or multiple (20% have 4+ nodules) well circumscribed nodules, subcapsular, gray-white, occasionally green; often less than 5 mm

Micro: periportal small clusters of modestly dilated bile ducts, often angulated, in fibrous stroma; may contain intraluminal bile; epithelial cells are bland; usually no/minimal inflammatory infiltrate, no atypia

Positive stains: mucin (variable)

Metabolic diseases

Metabolic diseases-general

Diagnosis may require special stains, electron microscopy, biochemical examination

Due to congenital inborn errors of metabolism or acquired

Alpha-1-antitrypsin deficiency

Common cause of neonatal cholestasis

Autosomal recessive disease, causing low serum levels of alpha-1-antitrypsin (AAT), and leading to emphysema (80%) and liver disease

AAT is a small, 394 amino acid, plasma glycoprotein, synthesized predominantly by hepatocytes, encoded by a gene on #14

AAT is a protease inhibitor (Pi), which inhibits neutrophilic elastase released at sites of inflammation; also inhibits trypsin

Although there are 75 AAT forms, PiMM (normal phenotype) is present in 90% of population

PiZZ: 1 per 7,000; have 10-15% of normal AAT levels, are at high risk for clinical disease; accumulate AAT variant Z in endoplasmic reticulum and have slowdown in degradation pathway, but only 10% get clinical disease

PiZZ hepatic syndromes range from neonatal hepatitis (10%), biliary atresia (intra- or extrahepatic), fibrosis, childhood cirrhosis; 2% develop hepatocellular carcinoma, not always associated with cirrhosis

PiMZ: intermediate plasma levels of AAT (expression of alleles is autosomal codominant)

Pi-null: rare variant with no detectable serum AAT

Pi-S: low serum AAT but no disease

AAT deficiency variants: secretory protein does not move from endoplasmic reticulum to Golgi; for PiZ, is due to single AA substitution, causing abnormal folding, blocking its movement along the remainder of the secretory pathway

Diagnosis: serum protein electrophoresis; liver biopsy to determine extent of histologic damage

Treatment: liver transplantation, avoid cigarette smoking (which causes earlier and more severe emphysema)

Micro: round to oval cytoplasmic eosinophilic globular inclusions in periportal hepatocytes; rare Mallory bodies and fatty change; also hepatocellular degeneration, giant cell formation, cholestasis and cholangitis, portal fibrosis and cirrhosis

Positive stains: AAT immunostains; inclusions are strongly PAS+ and diastase resistant

EM: granular material in dilated endoplasmic reticulum

DD: AAT that is present in damaged and regenerating hepatocytes (usually diffuse granules, not periportal, no globules, PAS negative), AAT+ globules present in alcoholic hepatitis

Cystic fibrosis

Most common lethal genetic disease in US of whites - affects 1 per 2000-4500 newborns

1 in 20 in US are carriers; most common mutation is #708 of protein that regulates chloride ion transport on chromosome #7 (seen in 70% with disease)

Mutations cause reduced chloride ion in secretions, thicker respiratory secretions, upper respiratory infections, late pancreatic insufficiency; also cause defective cilia and infertility, meconium ileus (5-10%), intussusception

May present as neonatal cholestasis, although most patients have no clinical evidence of liver disease

Treatment: liver transplantation (if end stage liver disease)

Gross: emphysema, bronchiectasis, abscess, fibrosis

Micro: macrovesicular steatosis, focal biliary cirrhosis (focal findings of inspissated granular eosinophilic material within portal bile ductules, chronic inflammatory infiltrate in portal tract, bile duct proliferation), cirrhosis (10% by age 25)

EM: filamentous material in bile ducts

Erythropoietic protoporphyria

Micro: deep brown colored bile in canaliculi, bile ducts and Kupffer cells with red “Maltese cross” under polarized light

EM: star-burst crystalline array

Familial apolipoprotein A-I amyloidosis

Apo A-I is major protein constituent of plasma high density lipoprotein; is synthesized in liver and intestine

Are at least 4 different amyloidogenic Apo A-I mutations

Treatment: liver transplant slows disease progression

Case reports of 2 sisters with liver transplants, Mod Path 2001;14:577

Micro: often striking liver parenchymal involvement by large patches of amyloid replacing hepatic lobules, separating hepatic cords, accentuation around central veins, involving portal triads, hilar soft tissue; no involvement of hilar nerve branches or vagus nerve

Positive stains: Congo red

Galactosemia

Micro: hepatocellular degeneration with focal fatty change, particularly in regenerative nodules; pseudorosettes, cholestasis, fibrosis, cirrhosis

EM: cholestasis, lipid droplets, increased endoplasmic reticulum, abnormal mitochondria

Gaucher’s disease

Micro: enlarged Kupffer cells and portal macrophages with “crinkled paper” cytoplasm

EM: intralysosomal tubular inclusions

Glycogen storage disease

Type I

Micro: mosaic pattern due to enlarged hepatocytes compressing sinusoids; fatty change, hyperglycogenated nuclei

EM: increased cytoplasmic glycogen, lipid droplets, glycogenated nuclei

Type Ia

Also called von Gierke disease

Rare; due to absence of glucose-6-phosphatase, which is required for gluconeogenesis and glycogenolysis

Symptoms: hypoglycemia and marked hepatomegaly in first year of life; later-short stature, chronic lactic acidosis, focal segmental glomerulosclerosis, hepatic adenomas, iron deficiency

Treatment: liver transplant

Case report of 28 year old woman with multiple hepatic adenomas, Archives 2003;127:e402

Gross: enlarged, pale liver; may have variable sized tumor nodules

Micro: large hepatocytes with prominent cell membrane and glycogenated nuclei; PAS+ accumulated glycogen; rarely contain Mallory’s hyaline and steatosis in hepatic adenomas

Type II

Micro: increased hepatocellular glycogen

EM: intralysosomal glycogen

Type III

Micro: mosaic pattern due to enlarged hepatocytes compressing sinusoids; fatty change, hyperglycogenated nuclei

EM: increased cytoplasmic glycogen, lipid droplets, glycogenated nuclei

Type IV

Also called amylopectinosis, Andersen disease

Rare, autosomal recessive, caused by deficiency of glycogen branching enzyme on 3p14

Classic form: progressive hepatic fibrosis through age 18 months causing hepatosplenomegaly, failure to thrive, death by 5 years

Rare nonprogressive form: no cirrhosis, live to adulthood

Neuromuscular form: severe hypotonia at birth causing death or myopathy in late childhood or nervous system dysfunction as adults

Case report of 10 month old male with massive hepatomegaly, Archives 2002;126:630

Diagnosis: amylopectin-like material in tissue; deficiency of branching enzyme activity

Treatment: liver transplantation

Micro: basophilic intracytoplasmic inclusions, PAS+, diastase partially resistant

EM: filamentous nonbranching cytoplasmic aggregates

DD: Lafora disease (similar inclusions but not coarsely clumped, older age with epilepsy, myoclonus, dementia)

GM2 gangliosidosis

Micro: normal

EM: “zebra bodies” - membrane-bound laminated inclusions

Heme oxygenase-1 deficiency

Enzyme degrades heme into biliverdin, carbon monoxide and free iron; also is anti-oxidant

Case report of 6 year old boy with growth retardation, anemia, other laboratory abnormalities, Hum Path 2002;33:125

Micro: amyloid present in liver and adrenal glands, mesangioproliferative glomerular changes in kidney, fatty streaks and fibrous plaques in aorta

Hemochromatosis

General

Excessive accumulation of iron, usually deposited in liver, pancreas and heart

Either primary or secondary

Normal iron pool is 2-6 gm with 0.5 g in liver and 98% of that in hepatocytes

Primary hemochromatosis

Autosomal recessive disorder of excessive iron storage; may exceed 50g in liver (normal 2-6 g)

Most common single-gene disorder in whites

80% males, because menstruation and pregnancy delay iron accumulation in women

1/220 of Northern European ancestry are homozygous for mutation; 1/11 are heterozygous; thus disease is very common

Pathophysiology: due to mutation on transferrin receptor binding protein HFE (formerly called HLA-H) on 6p, close to HLA gene, and in linkage disequilibrium with HLA-A3

Common mutation (83% of primary cases) is cysteine to tyrosine at amino acid 282 (C282Y), which inactivates the protein and causes excess iron absorption of 3-4 mg/day vs. 1-2 mg/day normal; normal HFE down regulates transferrin; loss of HFE causes up regulation of transferrin; other mutation is H63D (3-7% of cases) and compound heterozygotes (1-4%)

Excessive iron cannot be eliminated, and is directly toxic, due to lipid peroxidation, stimulation of collagen, interactions of iron with DNA

Mutation causes net iron accumulation of 0.5 to 1.0 g iron/year, although penetrance is less than 100%

Symptoms: after accumulation of 20 g of iron; usually age 40+; primarily micronodular cirrhosis (100%), diabetes mellitus (deposition in pancreas) and skin pigmentation (65%); also hemosiderin deposition in myocardium, pituitary, adrenal, thyroid, parathyroid gland, joints, skin; eventually cirrhosis and pancreatic fibrosis; high risk for hepatocellular carcinoma (200x, 20% risk)

Diagnosis: screen for percent transferrin saturation (serum iron divided by total iron binding capacity); if repeatedly elevated, check serum ferritin; if elevated, do DNA testing for C282Y mutation; also screen family members of affected individuals

Hepatic iron index: micrograms iron per gram dry weight of liver / (55.846 x patient’s age)

Interpretation: >1.9 in non-cirrhotic liver is strongly suggestive of hereditary hemochromatosis, although only 93% sensitive; test is less specific in cirrhotic livers (some suggest raising cut-off to 4.2 in these patients); sampling variation can occur

Treatment: phlebotomy 1-2/week until serum ferritin is below 20-50 micrograms/L, then 3-6 times/year; with early treatment, life expectancy is normal

Gross: dark brown liver

Micro: liver - iron within hepatocytes, initially heavy periportal parenchymal iron deposition with sparing of Kupffer cells; iron distribution is pericanalicular, particularly in less involved areas; hepatocytes otherwise normal; no inflammation, no fibrosis

pancreas - intensely pigmented, diffuse interstitial fibrosis

heart - enlarged with hemosiderin within myocardial fibers

joints - acute synovitis, calcium pyrophosphate deposition (pseudogout)

skin - hemosiderin in dermal macrophages and fibroblasts, also increased melanin production; causes slate-gray skin

testes - small, atrophic testis, due to hypothalamic-pituitary derangement; minimal pigment deposition

Positive stains: Prussian blue (iron stain)

Secondary hemochromatosis

Due to transfusions (secondary to hemodialysis, aplastic anemia, sickle cell anemia, myelodysplasia, leukemia), ineffective erythropoiesis with increased erythroid activity (secondary to beta thallasemia, sideroblastic anemia, pyruvate kinase deficiency), increased oral intake of iron or iron dextran injections, congenital atransferrinemia, chronic liver disease (alcoholism, porphyria cutanea tarda)

Note: transfusions alone are usually not sufficient to cause systemic hemosiderosis

Bantu siderosis: due to alcohol fermented in iron utensils in sub-Saharan Africa

Micro: iron is mainly in Kupffer cells, not hepatocytes, at least initially, and is primarily centrilobular; eventually iron is present in hepatocytes, which are otherwise normal

Neonatal hemochromatosis

Autosomal recessive, but probably unrelated to adult-type hemochromatosis, although similar histologic patterns

Liver failure soon after birth due to excess iron in liver; also iron deposition in pancreas, thyroid, kidney, GI tract

DD: massive necrosis (also has excess hepatic iron)

Hereditary fructose intolerance

Micro: hepatocellular degeneration with focal fatty change, particularly in regenerative nodules; pseudorosettes, cholestasis, fibrosis, cirrhosis

EM: lucent partially membrane bound areas of cytoplasm (“fructose holes”), concentric arrays of endoplasmic reticulum and glycogen

Hereditary hepatic coproporphyria

Case report of 35 year old woman with rapidly progressive liver cirrhosis, Archives 2002;126:751

Hereditary tyrosinemia

Type I

Autosomal recessive disease caused by deficiency of fumarylacetoacetate hydrolase, the last enzyme in the catabolic pathway of tyrosine; high prevalence in eastern Quebec

May be severe, affecting liver, kidneys, nervous system, but also clinically heterogeneous, with no correlation between genotype and phenotype

Acute form causes hepatic failure in newborns and death by age 1 without treatment

Chronic form is milder, with chronic liver disease, renal tubular dysfunction, hypophosphatemia with rickets and increased risk for hepatocellular carcinoma

80% of patients have reversion of mutant alleles in hepatocytes, associated with better prognosis (no dysplasia, no carcinoma)

Treatment: 2-(2-nitro-4-trifluoro-methylbenzoyl)-1,3-cyclohexanedione (NTBC) reduces accumulation of toxic metabolites

Micro: hepatocellular degeneration with focal fatty change, particularly in regenerative nodules; pseudorosettes, cholestasis, fibrosis, cirrhosis

EM: cholestasis, lipid droplets, increased endoplasmic reticulum, abnormal mitochondria

References: Hum Path 2003;34:1313 (mutation reversion)

Mucopolysaccharidosis

Hurler’s disease: mucopolysaccharidosis type 1

Micro: no abnormalities

Positive stains: colloidal iron stains mucosubstances in Kupffer cells and hepatocytes

EM: lysosomes in all cells contain flocculent material

Niemann-Pick disease

Micro: foamy Kupffer cells and hepatocytes

EM: intralysosomal myelin-like inclusions

Porphyria cutanea tarda

Micro: needle-shaped inclusions within hepatocytes

EM: needle-shaped inclusions within hepatocytes

Primary hyperoxaluria

Case report of 39 year old woman with recurrent nephrolithiasis, Archives 2002;126:1250

Autosomal recessive, either type 1 (defect/absence of alanine-glyoxalate aminotransferase on 2q37.3; patients have variable clinical presentation from end stage renal disease to occasional kidney stones) or type 2 (absence of glyoxylate reductase activity at #9)

Pathophysiology: oxalate is a metabolic end product normally excreted by kidneys; type 1 or 2 disease causes increased oxalate synthesis and excretion, eventually deposition of insoluble calcium oxalate in kidney, bones, heart, arteries; in liver, deposited in portal areas and arterial media

Treatment: increase urine volume, pyridoxine, high phosphate diet

Micro: crystals are birefringent

DD of hyperoxaluria: increased Vitamin C, methoxyflurane, ethylene glycol, xylitol, chronic inflammatory bowel disease, small bowel resection, external biliary drainage

Wilson’s disease

Also called hepatolenticular degeneration

Autosomal recessive disorder affecting 1/30,000 people, causing accumulation of toxic levels of copper in tissues/organs, usually liver, brain, eye

Normal copper physiology: total body copper is 50-150g; 40% of ingested copper is absorbed in stomach and duodenum and transported to liver loosely bound to albumin; free copper dissociates and is transferred to hepatocytes, where it is incorporated into an alpha2 globulin to form ceruloplasmin, and resecreted into plasma; 99% of plasma copper is bound to ceruloplasmin

Senescent ceruloplasmin is endocytosed by the liver, degraded within lysosomes and excreted into bile, which is the primary route for copper elimination

The gene for Wilson’s disease is ATP7B on #13q, which encodes a transmembrane copper-transporting ATPase located on the hepatocyte canalicular membrane, which assists with copper excretion into bile; most affected patients are compound heterozygotes with different mutations of ATP7B on each allele that cause defective biliary excretion of copper; copper accumulates within the liver, exceeding the capacity for ceruloplasmin binding and causing liver injury

By age 5 years, nonceruloplasmin-bound copper causes acute or chronic liver disease, hemolytic anemia, deposition in putamen with frank psychosis or Parkinsonian symptoms, deposition in cornea, kidneys, bones, joints, parathyroid gland; also increased urinary excretion of copper (which is normally minimal)

Diagnosis: serum ceruloplasmin < 20 mg/dl, increased liver copper using rhodamine stain, urinary copper excretion > 50 micrograms/24 hours; biochemical determination from liver biopsy (can use formalin-fixed tissue, > 250 micrograms/g dry weight); serum copper levels are not helpful

Treatment: long-term copper chelation therapy with D-penicillamine; liver transplantation

Micro: liver - fatty change with vacuolated nucleus (due to glycogen or water), focal hepatocyte necrosis; an acute or chronic hepatitis may be present and mimic acute or chronic viral hepatitis; chronic hepatitis may have Mallory bodies; cirrhosis develops late; usually no/minimal eosinophils or plasma cells

Note: copper deposition is focal and may not be present on needle biopsies

Fulminant hepatitis: liver collapse with abundant lipofuscin due to degraded membrane fragments; remaining liver shows low-grade disease with fibrosis

brain - injury to putamen in basal ganglia

eye - Kayser-Fleischer rings (green to brown deposits of copper in Descemet’s membrane in limbus of cornea)

EM: microvesicular steatosis, glycogen nuclei, copper deposits, mitochondrial enlargement with increased matrical body size, increased matrix density, crystalline inclusions, swollen cristae that are separated due to flocculent material in cyst-like dilations

DD: copper accumulation also present in primary biliary cirrhosis, other cholestatic states

Wolman disease

Micro: foamy Kupffer cells and hepatocytes

EM: lipid droplets in hepatocytes and Kupffer cells; cholesterol clefts in Kupffer cells

Zellweger syndrome

Micro: nonspecific changes of hepatocyte degeneration

EM: no peroxisomes

General concepts

Ascites

Excess fluid in peritoneal cavity; usually detectable when 500 ml; usually serous, < 3 g/dl of protein

Presence of neutrophils suggests secondary infection, red blood cells suggests disseminated intraabdominal cancer, hydrothorax suggests long standing process with seepage through transdiaphragmatic lymphatics

Causes: sinusoidal hypertension drives fluid into space of Disse, normally removed by hepatic lymphatics; ascites is promoted by hypoalbuminemia; cirrhosis, portal hypertension

Cirrhosis-general

Defined as diffuse nodulation of liver, due to fibrous bands subdividing liver into regenerative nodules

All three features must be present: congenital hepatic fibrosis lacks regenerative nodules, focal nodular hyperplasia lacks diffuse nodulation, nodular regenerative hyperplasia lacks fibrous bands

Fibrosis is usually considered irreversible (regression rare in schistosomiasis, hemochromatosis) and alters patterns of blood flow and hepatocyte perfusion; initially around portal tracts, central vein or within space of Disse; later subdivides liver into nodules of regenerating hepatocytes surrounded by scar tissue (cirrhosis)

Nodules tend to increase in size over time

Represents the final common pathway of causes listed below; difficult to determine cause once present

Causes: alcoholic liver disease (60%), viral hepatitis (10%), biliary disease (5%), primary hemochromatosis (5%), idiopathic (5%), rare causes are Wilson’s disease, alpha-1-antitrypsin deficiency, galactosemia or tyrosinosis in children, cancer, drugs, syphilis, severe cardiac disease (cardiac cirrhosis), jejunoileal bypass, extensive small bowel resection

Idiopathic cases are often nonalcoholic steatohepatitis (33%), autoimmune liver disease (22%), alcoholic liver disease (14%), Hum Path 2002;33:1098

Pathogenesis: normally interstitial collagen types I and III is present in portal tracts, around central veins and occasionally in space of Disse; reticulin along hepatocytes is composed of type IV collagen; in cirrhosis, type I and III collagen are deposited in lobule, creating septal tracts; new vascular channels form, but blood is shunted around the parenchyma; get loss of fenestrations in sinusoidal endothelial cells, sinusoidal space resembles a capillary more than a channel for exchange of solutes between hepatocytes and plasma; Ito cells (hepatic stellate cells with myofibroblastic features) produce excess collagen in cirrhosis; normally store vitamin A, but are activated during development of cirrhosis, lose their retinyl ester stores and transform into myofibroblast-like cells;

Collagen synthesis and deposition are due to chronic inflammation (TNF-alpha, TGF-beta, IL-1); cytokines from Kupffer cells, endothelial cells, bile duct cells and hepatocytes; also disruption of extracellular matrix and toxins

Ito cells also constrict sinusoidal vascular channels

Bile channels are obliterated due to disruption of interface between parenchyma and portal tracts, causing jaundice

Symptoms: none; also anorexia, weight loss, weakness, osteoporosis; late - frank debilitation, portal hypertension, hepatic failure (with new stress)

Hepatopulmonary syndrome: due to imbalances of pulmonary blood flow, causes further stress

Death due to progressive liver failure, portal hypertension complications, hepatocellular carcinoma

Regression: controversial topic; proponents argue that it may occur if therapy halts progression; suggested by delicate perforated septa (incomplete fibrous septa whose residual components form linear, usually curved structure), isolated thick collagen fibers (not visibly attached to portal structure, hepatic vein or septum), delicate periportal fibrous spikes (collagenous extensions from portal tracts without visible connection to other portal tracts or hepatic veins), portal tract remnants (artery/duct pairs, unaccompanied arteries, or unaccompanied ducts, usually with absent portal vein, usually have less portal tract collagen than normal), hepatic vein remnants with prolapsed hepatocytes within the lumen, hepatocytes within portal tracts or splitting septa (clusters/cords of hepatocytes 2 or more cells in thickness within portal tracts or wedged between layers of fibrous septa), minute regenerative nodules (small clusters of hepatocytes less than 10 cells in diameter mixed with ductules), aberrant parenchymal veins (veins within 5 hepatocyte diameters of portal tracts), Archives 2000;124:1599

Micro: disruption in architecture of entire liver (loss of normal central-portal relationships) with bridging fibrous septa (delicate bands, broad scars) and rounded parenchymal nodules of regenerating hepatocytes without central veins; also abnormal vasculature due to parenchymal damage and scarring

Hard to diagnose cases: fragmented specimens with rounded edges containing connective tissue (use Trichrome or reticulin stains to visualize), no normal portal tracts, irregular central veins, two cell thick plates, large cell change is suggestive

Biopsy: cannot distinguish cirrhosis from bridging fibrosis due to small sample size, although reticulin stain may confirm regenerative nodules based on cell plates 3+ cells thick; absence of regenerative activity or presence of normal portal tracts and central veins argues against diagnosis of cirrhosis; don’t call definite cirrhosis unless at least one complete regenerative nodule can be identified; cirrhotic liver biopsy often has multiple small fragments of hepatocytes with smooth rounded contour due to leaving fibrous tissue behind

Positive stains: reticulin stain and collagen stains may highlight disordered lobular features, cirrhotic fibrosis is strongly positive for vitronectin (Hum Path 2001;32:1356)

DD: localized subcapsular or parenchyma