Cytokeratin 5 (EP1601Y)

Cytokeratin 5 is an intermediate filament protein of 58 kD molecular weight within the cytokeratin family. It is a type II (basic) cytokeratin. Antibodies to this protein identify basal cells of squamous and glandular epithelia, myoepithelia, and mesothelium.1 Anti-cytokeratin 5 has been reported useful in the differential diagnosis of metastatic carcinoma in the pleura versus epithelioid mesothelioma.2 Epithelioid mesotheliomas are strongly positive in almost all cases, but a minority of pulmonary adenocarcinomas will show focal immunoreactivity.2 Almost all squamous cell carcinomas, half of transitional carcinomas, and many undifferentiated large cell carcinomas immunostain with anti-CK 5.3 Anti-CK 5, along with anti-p63, affords a high sensitivity and specificity for squamous differentiation. Myoepithelial cells of the breast,4,5 glandular epithelia, and basal cells of the prostate are labeled with anti-CK 5.6 This antibody, along with anti-CK 14, has found application in identifying basal-like breast carcinoma.5,7