Cytokeratin 5 (CK5, K5)

Stains
Cytokeratin 5 (CK5, K5)

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

Revised: 4 December 2015, last major update October 2013

Copyright: (c) 2003-2015, PathologyOutlines.com, Inc.

PubMed Search: ck5[title]

Table of Contents

Cite this page: Cytokeratin 5 (CK5, K5). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/stainsck5.html. Accessed July 12th, 2017.

Definition / general

Molecular weight is 58 kDa
Major partner is CK14, but related to cytokeratin 6 (antibodies are often to CK5/6)
Common antibody is 34BE12
Mutations may cause epidermolysis bullosa simplex (Hum Mutat 2006;27:719), Dowling-Degos disease (Am J Hum Genet 2006;78:510)
Important in tooth enamel formation (J Biol Chem 2003;278:20293)

Interpretation

Diffuse cytoplasmic staining with perinuclear enhancement (Am J Surg Pathol 2001;25:43)

Uses by pathologists

Helps defines a basal-like subtype of invasive ductal carcinoma of the breast that is usually CK5/6+, ER-, PR-, HER2-, EGFR+ with poorer prognosis (Clin Cancer Res 2006;12:1533); associated with premenopausal African American women (JAMA 2006;295:2492), BRCA1 (J Natl Cancer Inst 2003;95:1482, Mod Pathol 2005;18:1321) and brain metastases (Am J Surg Pathol 2006;30:1097)
Defines a DCIS subtype with poorer prognosis (Hum Pathol 2007;38:197)
Distinguish breast usual ductal hyperplasia (strong staining) from solid papillary DCIS (negative, Hum Pathol 2006;37:787)
p63+ and CK5/6+ poorly differentiated metastatic carcinomas are likely to have squamous carcinoma primaries (Am J Clin Pathol 2001;116:823)
Distinguish epithelioid mesothelioma (CK5/6+ cytoplasmic staining with perinuclear enhancement) from lung adenocarcinoma (usually CK5/6 negative, Histopathology 2006;48:223); also in pleural effusions (Diagn Cytopathol 2006;34:801)
Distinguish cutaneous spindled squamous cell carcinoma (CK5/6+ in 100%) from superficial epithelioid sarcoma (rare focal positivity, J Cutan Pathol 2003;30:114)

Positive staining - normal

Breast myoepithelial cells, cornea (Exp Eye Res 2004;78:1137), mesothelium, nail unit of adults (Br J Dermatol 2004;151:362), prostate basal cells (J Pathol 2001;195:563) skin (basal layer), salivary glands (basal layer), spermatogenic cells (Mol Reprod Dev 2002;61:1), squamous epithelium (basal cells), urothelium (basal layer, Mol Cell Proteomics 2002;1:269)

Microscopic (histologic) images

Images hosted on Pathout server:

Contributed by Leica Microsystems, Biosystems Division-