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Stains
Cytokeratin 20 (CK20, K20)
Authors: Kara Hamilton, M.S., Nat Pernick, M.D., PathologyOutlines.com, Inc.
Revised: 2 March 2012, last major update - June 2009
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
Definition
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● Epithelial marker (MW 46 kDa), with restricted expression compared to CK7 (OMIM 608218)
Uses
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● General patterns (specificity varies)
(1) CK7+/CK20+ in carcinomas of bile duct (extrahepatic/gallbladder, often, Pathol Res Pract 2003;199:65), lung-mucinous bronchioloalveolar (AJCP 2004;122:421), pancreas (Cancer 2006;106:693 but see Archives 2000;124:1196)
-Urothelium (often, Archives 2001;125:921, Hum Path 2002;33:1136)
-Also primary mucinous tumors of ovary (74%), upper GI tract (78%), endocervix (88%, AJSP 2006;30:1130)
(2) CK7+/CK20- in carcinomas of bile duct (intrahepatic, Pathol Res Pract 2003;199:65), breast (Ann Diagn Pathol 1999;3:350), endocervical and endometrial adenocarcinoma (Int J Gynecol Pathol 2002;21:4), esophagus (distal, AJSP 2002;26:1213), lung (not mucinous bronchioloalveolar, BMC Cancer 2006;6:31), salivary gland (Pathol Int 2005;55:386), thyroid (Appl Immunohistochem Mol Morphol 2000;8:189)
-Also mesothelioma (Cancer 2001;92:2727)
(3) CK7-/CK20+ in carcinoma of colon (particularly early stage, Hum Path 2005;36:275)
-CK20 is less sensitive for poorly differentiated colonic carcinoma (Chin J Physiol 2006;49:298)
-Primary mucinous tumors of lower GI tract (79%, AJSP 2006;30:1130) and primary bladder adenocarcinomas (29%, AJSP 2001;25:1380)
(4) CK7-/CK20- in carcinomas of adrenal cortex and prostate (Mod Path 2000;13:962, free full text)
(5) To distinguish primary lung carcinoma (CK7+/CK20-) from metastatic colonic carcinoma to lung (CK7-/CK20+, BMC Cancer 2006;6:31)
(6) To help distinguish colon carcinoma (80% are CK20+) and poorly differentiated prostatic carcinoma (90% are CK20-) at biopsy (Archives 2007;131:599)
(7) To distinguish Merkel cell carcinoma (CK20+, dot like, TTF1-) and metastatic small cell carcinoma of lung (CK20-, TTF1+, Am J Dermatopathol 2006;28:99)
(8) To distinguish anal carcinoma (CK7+/CK20-) from downward growth of colorectal carcinoma (CK7-/CK20+, Archives 2001;125:1074)
(9) May confirm Barrett’s mucosa, which has strong diffuse CK7+ surface and crypt epithelium, strong CK20+ surface and superficial crypt staining
-Interpretation is affected by fixative (Hum Path 2005;36:58, but see Mod Path 2002;15:611-free full text)
-Pattern may help distinguish short segment Barrett’s from cardiac intestinal metaplasia (World J Gastroenterol 2005;11:6360)
(10) To distinguish Rathke cleft cysts and pituitary gland pars intermedia (CK8+, CK20+) from craniopharyngioma (CK8-, CK20-, Archives 2002;126:1174)
(11) To distinguish adenocarcinoma of distal esophagus (CK7+/CK19+: 90%, CK7+/CK20-: 74%) from proximal stomach (CK7+/CK19+: 44%, CK7+/CK20-: 24%, AJSP 2002;26:1213)
(12) To detect occult nodal tumor cells in colorectal adenocarcinoma (Hum Path 2006;37:1259, Br J Cancer 2006;95:218)
(13) RT-PCR to detect tumor cells of breast and colorectal carcinoma in blood (J Mol Diagn 2006;8:105)
(14) RT-PCR assessment in peritoneal wash may predict recurrence in gastric carcinoma (Oncol Rep 2007;17:667)
Urothelial carcinoma:
(a) CK20+ p53+ CD44- favors urothelial carcinoma in situ vs. reactive urothelium (AJSP 2001;25:1074)
(b) CIS shows CK20 staining of deep urothelial cells compared with surface cells only in non-neoplastic lesions (Appl Immunohistochem Mol Morphol 2006;14:260)
(c) CK20+ in voided urine by RT-PCR is sensitive and specific for bladder carcinoma (Clin Biochem 2004;37:803, J Egypt Natl Canc Inst 2006;18:82, but see J Urol 2003;169:86)
(d) In papillary urothelial neoplasms, CK20+ is associated with increasing tumor grade and stage in pTa and pT1 patients (Mod Path 2000;13:1315, free full text)
Positive stains - normal
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● Colon, Merkel cells, small intestine (AJSP 2004;28:1352), stomach
● Urothelium (umbrella cells, AJSP 2001;25:1074)
● Uterus
Positive stains – not carcinoma
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● Bladder intestinal metaplasia (Mod Path 2006;19:1395)
● Fibroepithelioma of Pinkus (Am J Dermatopathol 2007;29:7)
● GI carcinoid (25%)
● Hydatidiform mole (complete-100%, partial-50%, Gynecol Oncol 2002;87:34)
● Renal oncocytoma (dot-like pattern, J Histochem Cytochem 2001;49:919)
Positive stains - carcinoma
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● Ampullary (variable-AJSP 2005;29:359)
● Anal (variable-Br J Dermatol 2000;142:243, Cancer 2001;92:2045)
● Appendiceal epithelial neoplasms (benign and malignant, 100%, Hum Path 2005;36:1217)
● Biliary papillary tumors (benign and malignant, Hepatology 2006;44:1333)
● Colon (references above)
● Gastric (18-31%, Appl Immunohistochem Mol Morphol 2006;14:303, reduced if high levels of microsatellite instability, AJSP 2004;28:712)
● Hepatocellular (20% positive, Hum Path 2005;36:1226)
● Hepatoid adenocarcinoma (AJSP 2003;27:1302)
● Lung mucinous bronchioloalveolar (Hum Path 2002;33:915)
● Merkel cell (dot like, references above)
● Ovarian (Mod Path 2006;19:1421)
● Paget’s disease (secondary only-Br J Dermatol 2000;142:243)
● Pancreatic ductal (Cancer 2006;106:693)
● Prostatic (variable)
● Sinonasal adenocarcinoma (50%, Archives 2007;131:530)
● Small cell of major salivary glands (AJSP 2004;28:762), urothelial (references above)
● Vulvar Paget’s disease secondary to anorectal or urothelial carcinoma but not primary (Hum Path 2002;33:545)
Negative stains
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● Anal glands (Archives 2001;125:1074)
● Inverted urothelial papilloma (Hum Path 2004;35:1499)
Micro images
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anal glands are CK20- (fig 1C) but rectal adenocarcinoma is CK20+ (fig 2-)
Barrett’s-non classic staining pattern
cervical adenocarcinoma-intestinal type is CK20 neg (fig 1E)
colonic adenocarcinoma #1 (well differentiated); #2 (poorly differentiated); #3-metastatic; #4-primary (fig G) and metastatic to lung (fig H)
colonic medullary carcinoma (fig 4)
gastric carcinoma-poorly differentiated (fig 4a)
lung-nonmucinous bronchioloalveolar carcinoma is CK20 neg
lung-mucinous bronchioloalveolar carcinoma is CK20+
Merkel cell carcinoma #1; #2; #3-FNA
pancreatic ductal carcinoma is CK20 neg (fig 1f)
prostatic adenocarcinoma #1; #2 with positive staining of verumontanum
sinonasal adenocarcinoma-intestinal type (fig 4B)
testicular mucinous cystadenoma is CK20+ (fig 3a) but ovarian tumor is CK20-(fig 5a)
urothelial papillary neoplasm of LMP (fig 3C)
urothelial CIS is diffusely CK20+ (fig B)
urothelial carcinoma #1-high grade; #2-papillary-high grade (fig 5C); #3-papillary-low grade (fig 4C); #4-CK20+ primary and nodal metastasis; #5 (CK20 neg, uncommon)
Contributed by Leica Microsystems, Biosystems Division - colon (normal)-Cytokeratin 20 (PW31) with intense cytoplasmic staining
End of Stains > Cytokeratin 20 (CK20, K20)
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