Metaplastic breast carcinomas are basal-like tumours

Abstract

Recently, an immunohistochemical panel comprising antibodies against HER2, estrogen receptor (ER), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5 ⁄ 6 was reported to identify basal-like breast carcinomas, as defined by cDNA microarrays. Our aim was to analyse a series of metaplastic breast carcinomas (MBCs) using this panel plus two other basal markers (CK14 and p63) and progesterone receptor (PR), to define how frequently MBCs show a basal-like immunophenotype. Methods and results: Sixty-five cases were retrieved from the pathology archives of the authors’ institutions and reviewed by three of the authors. Immunohistochemistry with antibodies for HER2, ER, EGFR, CK5 ⁄ 6, CK14 and p63 was performed according to standard methods. All but six cases (91%) showed the typical immunoprofile of basal-like tumours (ER– and HER2–, EGFR+ and ⁄ or CK5 ⁄ 6+). When CK14 and p63 were added to the panel, two additional cases could be classified as basal-like. The majority of MBCs lacked PR, except 4 ⁄ 19 (21%) carcinomas with squamous metaplasia. Conclusions: Our results demonstrate that MBCs show a basal-like phenotype, regardless of the type of metaplastic elements. Moreover, as these neoplasms frequently overexpress EGFR (57%), patients with MBC may benefit from treatment with anti-EGFR drugs.