Cytokeratin 1 (CK1, K1)

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

Revised: 4 December 2015, last major update October 2013

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

PubMed Search: ck1[title]
Cite this page: Cytokeratin 1 (CK1, K1). website. Accessed February 19th, 2018.
Definition / general
Uses by pathologists
  • No significant clinical use by pathologists
Positive staining - normal
  • Endothelial cells, skin and other squamous epithelium (suprabasal spinous and granular layers), thymic Hassal’s corpuscle
Positive staining - disease
  • Angiosarcoma (73%), epithelioid hemangioendothelioma (100%), epithelioid sarcoma (70%), hemangioma (often), schwannoma (62%), squamous cell carcinomas-keratinizing, synovial sarcoma (28%), vascular tumors (greater in well versus poorly differentiated tumors)
Microscopic (histologic) images

Image hosted on

Eccrine sweat gland expression

Additional references