Stains & CD markers
Cytokeratins - uncommon


Topic Completed: 1 October 2013

Minor changes: 25 June 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: CK1[title], CK2[title], CK3[title], CK4[title], CK9, CK11, CK13[title], CK15, CK16, KL-1

Nat Pernick, M.D.
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Cite this page: Pernick N. Cytokeratins - uncommon. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsck1.html. Accessed September 20th, 2021.
Cytokeratin 1 (CK1)
  • Highest molecular weight keratin (67 - 68 kDa)
  • Produced by KRT1 gene in complex manner (PLoS Genet 2006;2:e93)
  • Associates with CK10
  • Keratin 1b is expressed in eccrine sweat glands (J Invest Dermatol 2005;125:428)
  • Reduced expression in HPV infection (Cancer Res 1990;50:3709)
  • Mutations are associated with:
  • 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)
  • References: Hum Pathol 2001;32:873, OMIM 139350
Cytokeratin 2 (CK2)
  • Molecular weight (CK2e) is 65.5 - 65.8 kDa
  • Associates with CK10
  • Mutations cause ichthyosis bullosa of Siemens (Br J Dermatol 2005;152:1353)
  • K2e (epidermis) and K2p (palate) are encoded by separate genes, with < 75% identity at primary structural level; thus, are not true isoforms, although they cannot be distinguished by conventional 2D electrophoresis
  • Uses by pathologists: no significant clinical use by pathologists
  • Positive staining - normal: skin (upper spinous and granular cells) (Br J Dermatol 1999;140:582)
  • References: OMIM 600194, Exp Cell Res 1992;202:132
Cytokeratin 3 (CK3)
  • Molecular weight is 64 - 65 kDa
  • Associates with CK12
  • Mutations in KRT3 gene may cause Meesmann corneal dystrophy (Cornea 2005;24:928)
  • Uses by pathologists: no significant clinical use by pathologists
  • Positive staining - normal: corneal epithelium (full thickness), limbus epithelium (suprabasal)
  • Negative staining: conjunctival epithelium
  • Reference: OMIM 148043
Cytokeratin 4 (CK4)
  • Molecular weight is 59 kDa
  • Associates with CK13
  • Downregulated in head and neck squamous cell carcinoma (Acta Otolaryngol 2006;126:967)
  • Uses by pathologists: no significant clinical use by pathologists
  • Case report: young man with novel mutation in the keratin 4 gene causing white sponge naevus (Br J Dermatol 2003;148:1125)
  • Positive staining - normal: suprabasal cells of nonkeratinized stratified squamous epithelium of esophagus and cornea; also anus, larynx, pharynx, tongue (J Biol Chem 1998;273:23912)
  • Reference: OMIM 123940
Cytokeratin 9 (CK9)
Cytokeratin 11 (CK11)
  • Very little information is present on CK11
  • Uses by pathologists: no significant clinical use by pathologists
  • Positive staining - normal: keratinizing epidermal squamous cells
Cytokeratin 13 (CK13)
  • Molecular weight is 53 kDa
  • Pairs with CK4
  • Marker of mature but nonkeratinized squamous epithelium
  • Downregulated in squamous cell carcinoma of head and neck and other sites (Oral Oncol 2005;41:183, Virchows Arch A Pathol Anat Histopathol 1991;418:249)
  • Sensitive marker for retinoid bioactivity in skin warts of renal transplant recipients (Arch Dermatol 2002;138:61)
  • Mutation causes familial white sponge nevus (J Dent Res 2001;80:919)
  • Cable piliated Burkholderia cepacia binds to cytokeratin 13 of epithelial cells (Infect Immun 2000;68:1787)
  • Uses by pathologists: no significant clinical use by pathologists
  • Positive staining - normal: suprabasal layers of noncornified stratified epithelium, including squamous (nonkeratinized) epithelia of cervix, esophagus, larynx, oral cavity, tonsils, urothelium and respiratory type epithelium; may be filled with mucoid material or foamy macrophages
  • Positive staining - disease: Brenner tumor; squamous metaplasia; squamous cell carcinoma (10%); urothelial carcinoma (well differentiated)
  • Negative staining: epidermis
  • References: J Dent Res 2001;80:919, OMIM 148065
Cytokeratin 15 (CK15)
Cytokeratin 16 (CK16)
Cytokeratin KL-1
Microscopic (histologic) images

Images hosted on other servers:

CK3: suprabasal staining
of limbus epithelium
cultured using
airlifting technique

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Image 01 Image 02