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CK5 Is More Sensitive Than CK5/6 in Identifying the “Basal-like” Phenotype of Breast Carcinoma

Rohit Bhargava MD, Sushil Beriwal MD, Kim McManus HT(ASCP), David J. Dabbs MD
DOI: http://dx.doi.org/10.1309/AJCP3KFF1LTYWQIY 724-730 First published online: 1 November 2008


Multiple immunohistochemical stains, including cytokeratin (CK)5/6, are used in a panel format to identify “basal-like” carcinomas. We set out to determine the sensitivity and specificity of the CK5 antibody (clone XM26) and compared its expression with that of CK5/6 (clone D5/16B4) in a variety of breast carcinoma cases. The study was performed on 3 breast carcinoma tissue microarrays (TMAs). TMA-1 consisted of 59 consecutive breast carcinoma cases. TMA-2 (n = 16) and TMA-3 (n = 11) consisted of basal-like breast carcinomas previously characterized morphologically and immunohistochemically at our institution. Of the 86 total cases, 20 were positive for CK5 and CK5/6, 14 were positive for CK5 only, and 52 were negative for both. The sensitivity of CK5 for identifying basal-like tumors was 97% compared with 59% for CK5/6. Both antibodies had comparable specificity of more than 95%. For positive cases, the percentage and intensity of staining was much higher with CK5 than with CK5/6 (P = .0001).

Key Words:
  • Cytokeratin 5
  • Cytokeratin 5/6
  • Breast basal-like carcinoma
  • Immunohistochemistry