Liver & intrahepatic bile ducts

Benign / nonneoplastic

Mesenchymal hamartoma



Last author update: 12 December 2022
Last staff update: 12 December 2022

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PubMed Search: Mesenchymal hamartoma


Bella Lingjia Liu, M.D.
Stephen C. Ward, M.D., Ph.D.
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Cite this page: Liu BL, Ward SC. Mesenchymal hamartoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/livertumormesenchymalhamart.html. Accessed February 6th, 2023.
Definition / general
  • Rare, benign hepatic lesion of young children
  • Primitive myxoid mesenchyme with benign dilated or branching bile ducts and clusters of normal appearing hepatocytes
Essential features
  • Second most common benign pediatric hepatic tumor after infantile hemangioma (Arch Pathol Lab Med 2006;130:1567)
  • 80% are diagnosed in infants and children < 2 years old (Arch Pathol Lab Med 2006;130:1567)
  • Excellent prognosis with complete resection; rare malignant transformation to embryonal sarcoma has been described
  • Variable proportions of mixed solid and cystic areas with disorganized arrangement of primitive mesenchyme, benign bile ducts and normal appearing hepatocytes (Hepat Oncol 2020;7:HEP19)
  • Associated with recurrent genetic alterations resulting in activation of chromosome 19 microRNA cluster (C19MC)
Terminology
  • Hepatic or giant lymphangiomas, bile cell fibroadenomas, cavernous lympangiomatoid tumors, hepatic cystic hamartoma (SA J Radiol 2020;24:1891)
ICD coding
  • ICD-10: D13.4 - benign neoplasm of liver
Epidemiology
Sites
  • Pediatric patients: right liver lobe predilection
  • Adults: similar involvement of both liver lobes (Hum Pathol 2002;33:893)
Pathophysiology
Clinical features
  • Usually sporadic; associations with Beckwith-Wiedemann syndrome and placental mesenchymal dysplasia have been described (Pediatr Dev Pathol 2014;17:75)
  • Typically present as an enlarging abdominal mass
    • Small lesions are usually asymptomatic
    • Large lesions may be associated with abdominal pain, abdominal distention, vomiting, poor weight gain, respiratory distress, cardiac failure and ascites (J Clin Neonatol 2012;1:211)
  • Rarely, may undergo malignant transformation to undifferentiated embryonal sarcoma (Hepat Oncol 2020;7:HEP19)
Diagnosis
  • Histologic examination
Laboratory
Radiology description
  • Complex cystic mass with internal septations on ultrasound
  • Complex cystic mass with septal and solid stromal enhancement on CT or MRI
Radiology images

Images hosted on other servers:

CT scans

Case reports
Treatment
Gross description
  • Usually solitary; rarely with intrahepatic satellite nodules
  • Well circumscribed mass with mixed solid and cystic areas
  • Size ranging from a few centimeters to 30 cm
  • Usually no necrosis, hemorrhage or calcification
  • Becomes fibrotic with age
Gross images

Contributed by Bella Lingjia Liu, M.D.

Cut surface of the tumor



Images hosted on other servers:

Cut surface of the tumor

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Bella Lingjia Liu, M.D. and Ankur R. Sangoi, M.D. (Case #61)
Solid area

Solid area

Entrapped benign hepatocytes

Entrapped benign hepatocytes

Bile ducts

Bile ducts

Cystic area Cystic area

Cystic area


Branching bile ducts

Branching bile ducts

Disorganized hepatic architecture Disorganized hepatic architecture

Disorganized hepatic architecture

Dilated and branching bile ducts

Dilated and branching bile ducts

Hepatocytes in myxoid stroma

Hepatocytes in myxoid stroma


Bland bile duct structures

Bland bile duct structures

CK7

CK7

Vimentin

Vimentin

Cytology description
Cytology images

Images hosted on other servers:
Cytology

Hepatic mesenchymal hamartoma

Positive stains
Negative stains
Electron microscopy description
  • Myofibroblastic features
Molecular / cytogenetics description
Sample pathology report
  • Liver mass, resection specimen:
    • Hepatic mesenchymal hamartoma (16 cm) (see comment)
    • Comment: The neoplasm consists of scattered dilated and angulated ducts lined by cuboidal epithelium in a background of loose myxoid tissue with scattered bland spindle cells. Small islands of entrapped benign hepatic parenchyma are noted. No necrosis or mitotic figures are identified. The tumor is located 0.5 cm from the nearest surgical resection margin. Hilar structures are free of tumor. The adjacent hepatic parenchyma shows congestion and mild portal fibrosis, portal inflammation and proliferation of bile ductules consistent with adjacent mass effect.

  • Liver, needle biopsy specimen:
    • Hepatic mesenchymal hamartoma (see comment)
    • Comment: Lesion is characterized by loose myxomatous stroma with scattered bland stellate shaped mesenchymal cells, branching bile ducts and scattered hepatocytes. The findings are consistent with hepatic mesenchymal hamartoma.
Differential diagnosis
  • Myxomatous infantile hemangioma / hemangioendothelioma:
    • Most common hepatic mesenchymal tumor in childhood
    • Majority affects infants < 6 months old, with slight female predominance
    • Can be well circumscribed or infiltrative (35%)
      • Type 1 with proliferation of capillary-like vascular spaces lined by bland endothelial cells with no / rare mitotic figures and no malignant spindle cell component
      • Type 2 with irregular branching vascular structures lined by pleomorphic, hyperchromatic endothelial cells with frequent mitotic activity
    • Positive for GLUT1, CD31, CD34 and factor VIII related antigen
  • Undifferentiated embryonal sarcoma:
    • Third most common pediatric hepatic tumor, mainly affecting children 6 - 10 years old
    • Anaplastic, bizarre tumor cells with prominent eosinophilic cytoplasm and PAS+ diastase resistant hyaline globules
  • Mixed epithelial mesenchymal hepatoblastoma:
    • Epithelial component with embryonal and fetal hepatocytes with high N:C ratios and marked cellular atypia
    • Mesenchymal component has spindle cells, osteoid, cartilage
Board review style question #1

A 9 month old boy with abdominal distention was found to have a 7.3 x 6.5 x 3.4 cm complex cystic mass in the right liver. Histologic examination of the cyst wall revealed the findings shown above. What is the diagnosis?

  1. Angiomyolipoma
  2. Bile duct hamartoma
  3. Hepatic mesenchymal hamartoma
  4. Myxomatous infantile hemangioma / hemangioendothelioma
  5. Undifferentiated embryonal sarcoma
Board review style answer #1
C. Hepatic mesenchymal hamartoma

Comment Here

Reference: Mesenchymal hamartoma
Board review style question #2
Which of the following statements regarding hepatic mesenchymal hamartoma is true?

  1. Associated with recurrent genetic alteration resulting in activation of chromosome 19 microRNA cluster (C19MC)
  2. Has variable proportions of cystic and solid components and is commonly associated with necrosis with frequent mitotic figures and cytological atypia
  3. It is the second most common benign hepatic tumor, mainly affecting adults between 20 - 50 years old
  4. Positive for GLUT1 in the epithelial components
  5. Radiation therapy is the best treatment method
Board review style answer #2
A. Associated with recurrent genetic alteration resulting in activation of chromosome 19 microRNA cluster (C19MC)

Comment Here

Reference: Mesenchymal hamartoma
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