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Cytokeratin 5/6 (CK 5/6)

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  • Cytokeratin 5/6 (CK 5/6) staining basal cells in a benign prostate gland.
  • Cytokeratin 5/6 expression in eccrine ducts and coil. Note that while both layers of the eccrine duct express CK 5/6, only the basal layer stains positively with CK 5/6 in the eccrine coil.
  • Cytokeratin 5/6 expression in normal parotid gland
  • Cytokeratin 5/6 expression in normal parotid gland



  • 34BE12

Technical InfoEdit

Staining PatternEdit

Expression in Normal TissuesEdit

  • Cornea
  • Breast myoepithelial cells
  • Mesothelium
  • Adult nail unit
  • Basal layer of: prostate, skin, urothelium, spermatogenic cells, and salivary glands
  • Esophagus
  • Epidermal and epithelial glands
  • Oral mucosa
  • Stomach

Expression in Neoplastic EntitiesEdit

  • Usual ductal hyperplasia[1]
  • Adrenal cortical adenoma[2]
  • Adrenal cortical carcinoma[2]
  • Lung (adenocarcinoma[3] and squamous[4])

Expression in Non-Neoplastic EntitiesEdit

  • Psoriasis
  • Cutaneous amyloidosis[5]

Practical Uses / PanelsEdit

  • Usual ductal hyperplasia vs. DCIS[1]
  • Epitheliod mesothelioma vs. lung adenocarcinoma[6]
  • Has prognostic value when used with EGFR to determine if a triple negative breast carcinoma (ER-, PR-, Her2-) is expressing basal cell antigens (Basal-like breast carcinomas are CK5/6+ and EGFR+ and have a worse prognosis)[7]
  • Sinonasal Undifferentiated Carcinoma (SNUC) vs Squamous Cell Carcinoma (keratinizing and non-keratinizing types) in the sinonasal tract.[8]

Common PitfallsEdit

Related Links/Other ResourcesEdit


  1. 1.0 1.1 Rabban JT, Koerner FC, Lerwill MF. Solid papillary ductal carcinoma in situ versus usual ductal hyperplasia in the breast: a potentially difficult distinction resolved by cytokeratin 5/6. Hum Pathol. 2006;37(7):787-93
  2. 2.0 2.1 Wieneke JA, Thompson LD, Heffess CS. Adrenal cortical neoplasms in the pediatric population: a clinicpathologic and immunophenotypic analysis of 83 patients. Am J Surg Pathol. 2003;27(7):867-81
  3. Camilo R, Capelozzi VL, Siqueira SA, Del Carlo Bernardi F. Expression of p63, keratin 5/6, keratin 7, and surfactant-A in non-small cell lung carcinomas. Hum Pathol. 2006, 37(5):542-6
  4. Miettinen M, Sarlomo-Rikala M. Expression of calretinin, thrombomodulin, keratin 5, and mesothelin in lung carcinomas of different types: an immunohistochemical analysis of 596 tumors in comparison with epithelioid mesotheliomas of the pleura. Am J Surg Pathol. 2003;27(2):150-8
  5. Chang YT, Liu HN, Wang WJ, Lee DD, Tsai SF. A study of cytokeratin profiles in localized cutaneous amyloids. Arch Dermatol Res. 2004;296(2):83-8
  6. King JE, Thatcher N, Pickering CA, Hasleton PS. Sensitivity and specificity of immunohistochemical markers used in the diagnosis of epithelioid mesothelioma: a detailed systematic analysis using published data. Histopathology. 2006;48(3):223-32
  7. BMC Cancer. 2007 Jul 24;7:134.
  8. Franchi A, Moroni M, Massi D, Paglierani M, Santucci M. Sinonasal undifferentiated carcinoma, nasopharyngeal-type undifferentiated carcinoma, and keratinizing and nonkeratinizing squamous cell carcinoma express different cytokeratin patterns. Am J Surg Pathol. 2002 Dec;26(12):1597-604.

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