Cytokeratin 7 (CK7, K7)

Author: Nat Pernick, M.D. (see Authors page)

Revised: 15 April 2016, last major update December 2011

Copyright: (c) 2003-2016,, Inc.

PubMed Search: CK7
Cite this page: Cytokeratin 7 (CK7, K7). website. Accessed February 23rd, 2018.
Definition / general
  • Type II keratin of simple nonkeratinizing epithelia (OMIM 148059); molecular weight 54 kDa
  • Found in breast, lung, ovary and urothelium, but usually NOT in GI or stratified squamous epithelium
Uses by pathologists
Microscopic (histologic) images

Images hosted on Pathout server:

Ampullary adenocarcinoma

Breast-metaplastic carcinoma

Cardiac myxoma with glandular differentiation

Heart: myxoma

Liver: hepatocellular carcinoma, fibrolamellar variant

Lung adenocarcinoma: metastatic to ovary

Melanoma (uterus)

Nasal cavity: seromucinous hamartoma

Prostate: left-nephrogenic adenoma

Renal cell carcinomas (left to right): papillary-solid variant; tubulocystic

Ureter (normal)-Cytokeratin 7 (RN7) with
intense cytoplasmic staining (contributed
by Leica Microsystems, Biosystems Division)

Urethra: clear cell adenocarcinoma

Urothelial carcinoma: with glandular differentiation (fig 4)

Images hosted on other servers:

Anal glands (left-fig E) and transitional zone (right, fig 1B) are CK7+

Anal gland carcinoma is CK7+ (fig C)

Bladder: carcinoid and urothelium are CK7+ (fig F)

Bladder (left to right): plasmacytoid carcinoma, urachal mucinous cystadenocarcinoma

Bladder/urethra: clear cell adenocarcinoma

Breast: Left-cylindroma; right-Paget's disease

Cervical adenocarcinoma: Left-intestinal type (fig C); right-signet ring type (fig C)

Cholangiocarcinoma: extrahepatic
(fig C) and gallbladder (fig A)

Colonic and lung carcinoma (fig D-F)

Endometrioid adenocarcinoma (fig C)

Kidney: left - chromophobe carcinoma-eosinophilic variant is CK7+ (fig 2C); right - oncocytoma has scattered CK7+ cells (fig 6)

Nasal cavity: inverted papilloma

Ovarian mucinous cystadenoma is CK7+ (5B),
but testicular mucinous cystadenoma (fig 3B)
and colonic epithelium (fig 4B) are negative

Pancreas: ductal adenocarcinoma (fig E)

Penis/scrotum: mucoid cyst

Prostate: left-nephrogenic adenoma;
right-adenocarcinoma (occasional CK7+ cells)

Images hosted on
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Barrett's esophagus (fig B)

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Bladder: intestinal meteaplasia
and cystitis glandularis
(typical staining)

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Cholangiocarcinoma: intrahepatic (fig A)

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Choroid plexus papilloma

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Endolymphatic sac tumor (fig A)

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Kidney: metanephric adenoma,
papillary carcinoma, Wilm's

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Lung adenocarcinoma: non-mucinous bronchioloalveolar (fig C); mucinous bronchioloalveolar (fig C)

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Meningioma of middle ear / temporal bone

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Mesothelioma with rhabdoid features (fig C)

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Middle ear adenoma

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Renal cell carcinomas (left to right): papillary (fig 3B); chromophobe

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Salivary gland carcinomas (left to right): mucoepidermoid are CK7+ (fig B, E); adenoid cystic (fig B, E); salivary duct (fig B, E)

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Seminal vesicle adenocarcinoma

Skin: left-Mercel cell carcinoma; right-various tumors

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Various carcinomas (left to right): pancreatic-fig 1A, cholangiocarcinoma-fig 1C, urothelial-fig 1E; breast-fig 3A, ovary-fig 3C, lung-fig 3E, endometrium-fig 3G; colon-fig 4A, Merkel cell-fig 4C

Images hosted on Flickr:
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Nasal cavity: respiratory epithelial
adenomatoid hamartoma

Positive staining - normal
Positive staining - not malignant
Positive staining - malignant
Negative staining