Bilateral apocrine carcinoma of the breast - Molecular and immunocytochemical evidence for two independent primary tumours

Apocrine carcinoma is an uncommon variant of breast cancer. The frequency o f bilaterality in patients who have apocrine carcinoma in one breast is not significantly different from that fur bilateral mammary carcinomas in gene ral, but bilateral apocrine carcinomas are very uncommon. We report on a bi lateral apocrine carcinoma of the breast in a 74-year-old woman. The apocri ne differentiation in both tumours was confirmed by the positivity of the c ytoplasmic granules for PAS after diastase digestion and immunoreactivity f or GCDFP-15 and sialyl-Tn. The tumour in the right breast showed immunohist ochemical expression of p53, and a mutation was demonstrated by PCR-SSCP; t he tumour in the left breast was negative for p53 on immunohistochemistry, and no mutation was found at the molecular level. c-erbB2 expression was no t detected in the right tumour but there was overexpression (at the cell me mbrane) in the left tumour. Both tumours were aneuploid: the right tumour d isplayed multiple stemlines, whereas the left tumour had a triploid profile . Using the fluorescence in situ hybridization technique we demonstrated th at both tumours displayed chromosome 17 polysomy and numerical abnormalitie s of chromosome 1, polysomy in the right and monosomy in the left tumour. W e conclude that the two tumours are probably independent, as are most bilat eral carcinomas of the breast.