Increased alpha-B-crystallin expression in mammary metaplastic carcinomas

Aims: Mammary metaplastic carcinoma is a rare breast carcinoma, and may present diagnostic difficulty. Alpha-B-crystallin has been recently reported to be expressed in basal-like and metaplastic carcinomas. Methods and results: Thirty-three metaplastic carcinomas, 44 conventional high-grade carcinomas and 28 mesenchymal spindle cell neoplasms as controls were assessed for their expression of alpha B-crystallin and conventional basal-like phenotypic markers CK5/6, CK14, p63, c-kit and epidermal growth factor receptor (EGFR) by immunohistochemistry. Alpha-B-crystallin staining was positive in 68% of the metaplastic carcinomas with cytoplasmic staining in all tumour cell components. CK5/6, CK14, p63, c-kit and EGFR stained 43%, 68%, 45%, 21% and 25% of the metaplastic carcinomas, respectively. Combining these markers, 84% of the metaplastic carcinomas expressed either alpha B-crystallin or CK14. In comparison, only 14% (six cases) of conventional high-grade carcinoma and 7% (two cases) of mesenchymal spindle cell neoplasm expressed alpha B-crystallin; all but one of these carcinomas were ER/PR/HER2 triple-negative. Conclusions: Using alpha B-crystallin for diagnosis of metaplastic carcinoma gives a 68% sensitivity, 88% specificity, 74% positive predictive value, 85% negative predictive value and 78% accuracy. The sensitivity is enhanced to 84% with combinations of alpha B-crystallin/CK14. Alpha-B-crystallin may be used as an adjunct marker in the diagnosis of metaplastic carcinoma.