Syringocystadenoma papilliferum of the male nipple.

Syringocystadenoma papilliferum (SP) is a rare and benign cutaneous adnexal tumor, particularly infrequent in the breast, with only one previous case affecting a female nipple. The present tumor was located at the nipple of a 23-year-old man. This tumor consisted of several cysts and satisfied the characteristic microscopic features of SP: numerous papillary projections of double-layered glandular epithelium and a fibrovascular core with lymphoplasmacytic infiltration. Interestingly, many cysts were lined by stratified squamous epithelium with transition to glandular epithelium. Immunohistochemically, almost all structures were negative for gross cystic disease fluid protein-15, androgen receptor, estrogen receptor and progesterone receptor. The immunoprofiles of glandular epithelium were inadequate for the mature two-cell pattern of skin adnexal glands and mammary glands; most basal cuboidal cells lacked α-smooth muscle actin, and some of the luminal columnar cells were negative for cytokeratin 7 and cytokeratin 19. The clinical and pathological features of this uncommon tumor are presented, along with a review of the literature of SP of the breast.