Encapsulated apocrine papillary carcinoma of the breast: case report with clinicopathologic and immunohistochemical study.

We describe a case of encapsulated papillary carcinoma (EPC), apocrine variant in a 50-year-old woman. The patient presented a cystic lesion in her right breast, measuring 8 cm in diameter, containing three solid papillary nodules. A fine-needle aspiration showed isolated apocrine cells containing round nuclei, irregular nuclear membranes, fine chromatin, and prominent macronucleoli. The lesion was excised and showed a pure papillary apocrine carcinoma, which stained diffusely with GCDFP-15 and androgen receptors. The lesion was totally devoid of myoepithelial cells (smooth muscle actyn, p63, calponin, and collagen IV stains were negative). With MIB1 the proliferative activity was 10%. To the best of our knowledge, this is the first report of EPC apocrine variant with cytologic and immunohistochemical study. This lesion must be included in the list of apocrine lesions of the breast.