Cytokeratin 20 (CK20, K20)

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Stains & CD markers
Cytokeratin 20 (CK20, K20)

Author: Nat Pernick, M.D.

Last author update: 1 July 2013

Last staff update: 3 August 2023

Copyright: 2003-2024, PathologyOutlines.com, Inc.

PubMed Search: CK20

Table of Contents

Cite this page: Pernick N. Cytokeratin 20 (CK20, K20). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsCK20.html. Accessed December 29th, 2024.

Definition / general

Epithelial marker (MW 46 kDa) with restricted expression compared to CK7 (OMIM #608218)

Uses by pathologists

General patterns (specificity varies)
CK7+ / CK20+ in carcinomas of bile duct (extrahepatic / gallbladder, often, Pathol Res Pract 2003;199:65), lung-mucinous bronchioloalveolar (Am J Clin Pathol 2004;122:421), pancreas (Cancer 2006;106:693, but see Arch Pathol Lab Med 2000;124:1196)
- Urothelium (often, Arch Pathol Lab Med 2001;125:921, Hum Pathol 2002;33:1136)
- Also primary mucinous tumors of ovary (74%), upper GI tract (78%) and endocervix (88%, Am J Surg Pathol 2006;30:1130)
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 (Pathol Res Pract 2003;199:65), esophagus (distal, Am J Surg Pathol 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)
CK7- / CK20+ in carcinoma of colon (particularly early stage, Hum Pathol 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%, Am J Surg Pathol 2006;30:1130) and primary bladder adenocarcinomas (29%, Am J Surg Pathol 2001;25:1380)
CK7- / CK20- in carcinomas of adrenal cortex and prostate (Mod Pathol 2000;13:962)
To distinguish primary lung carcinoma (CK7+ / CK20-) from metastatic colonic carcinoma to lung (CK7- / CK20+, BMC Cancer 2006;6:31)
To help distinguish colon carcinoma (80% are CK20+) and poorly differentiated prostatic carcinoma (90% are CK20-) at biopsy (Arch Pathol Lab Med 2007;131:599)
To distinguish Merkel cell carcinoma (CK20+, dot-like, TTF1-) and metastatic small cell carcinoma of lung (CK20-, TTF1+, Am J Dermatopathol 2006;28:99)
To distinguish anal carcinoma (CK7+ / CK20-) from downward growth of colorectal carcinoma (CK7- / CK20+, Arch Pathol Lab Med 2001;125:1074)
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 Pathol 2005;36:58, but see Mod Pathol 2002;15:611)
- Pattern may help distinguish short segment Barrett’s from cardiac intestinal metaplasia (World J Gastroenterol 2005;11:6360)
To distinguish Rathke cleft cysts and pituitary gland pars intermedia (CK8+, CK20+) from craniopharyngioma (CK8-, CK20-, Arch Pathol Lab Med 2002;126:1174)
To distinguish adenocarcinoma of distal esophagus (CK7+ / CK19+: 90%, CK7+ / CK20-: 74%) from proximal stomach (CK7+ / CK19+: 44%, CK7+ / CK20-: 24%, Am J Surg Pathol 2002;26:1213)
To detect occult nodal tumor cells in colorectal adenocarcinoma (Hum Pathol 2006;37:1259, Br J Cancer 2006;95:218)
RT-PCR to detect tumor cells of breast and colorectal carcinoma in blood (J Mol Diagn 2006;8:105)
RT-PCR assessment in peritoneal wash may predict recurrence in gastric carcinoma (Oncol Rep 2007;17:667)

Urothelial carcinoma:
- CK20+ p53+ CD44- favors urothelial carcinoma in situ vs. reactive urothelium (Am J Surg Pathol 2001;25:1074)
- CIS shows CK20 staining of deep urothelial cells compared with surface cells only in non-neoplastic lesions (Appl Immunohistochem Mol Morphol 2006;14:260)
- 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)
- In papillary urothelial neoplasms, CK20+ is associated with increasing tumor grade and stage in pTa and pT1 patients (Mod Pathol 2000;13:1315)

Microscopic (histologic) images

Contributed by Leica Microsystems (Biosystems Division) and Andrey Bychkov, M.D., Ph.D.

Colon (normal):
CK20 (PW31) with
intense cytoplasmic
staining

Ovarian cancer

Urothelial carcinoma

Images hosted on other servers:

Colonic adenocarcinoma: #1-well differentiated; #2-poorly differentiated; #3-metastatic; #4-primary (fig G) and metastatic to lung (fig H)

PanIN lesions: CK20+ in grades 1, 2 and 3

Prostatic adenocarcinoma; #2 with positive staining of verumontanum

Tubular adenocarcinoma

Urothelial carcinoma, high grade

Positive staining - normal

Colon, Merkel cells, small intestine (Am J Surg Pathol 2004;28:1352) and stomach
Urothelium (umbrella cells, Am J Surg Pathol 2001;25:1074)
Uterus

Positive staining - not malignant

Bladder intestinal metaplasia (Mod Pathol 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 staining - malignant

Ampullary (variable, Am J Surg Pathol 2005;29:359)
Anal (variable-Br J Dermatol 2000;142:243, Cancer 2001;92:2045)
Appendiceal epithelial neoplasms (benign and malignant, 100%, Hum Pathol 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, Am J Surg Pathol 2004;28:712)
Hepatocellular (20% positive, Hum Pathol 2005;36:1226)
Hepatoid adenocarcinoma (Am J Surg Pathol 2003;27:1302)
Lung mucinous bronchioloalveolar (Hum Pathol 2002;33:915)
Merkel cell (dot like, references above)
Ovarian (Mod Pathol 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%, (Arch Pathol Lab Med 2007;131:530)
Small cell of major salivary glands (Am J Surg Pathol 2004;28:762), urothelial (references above)
Vulvar Paget’s disease secondary to anorectal or urothelial carcinoma but not primary (Hum Pathol 2002;33:545)

Negative staining

Anal glands (Arch Pathol Lab Med 2001;125:1074)
Inverted urothelial papilloma (Hum Pathol 2004;35:1499)

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