Syringocystadenoma papilliferum of the male breast.

A 39-year-old man presented with a 2-cm, mildly tender mass in the right breast of many years' duration. Microscopic examination showed a syringocystadenoma papilliferum. Because of its location in the breast, we studied the lesion for immunohistochemical markers for apocrine differentiation. Gross cystic disease fluid protein-15 (GCDFP-15) staining yielded negative results in the cystic luminal epithelial cells, whereas GCDFP-15 and lysozyme staining yielded strongly positive results in the epithelial cells of adjacent tubular apocrine glands. Focal strong lysozyme positivity was seen in the cystic luminal epithelial cells. These findings do not support apocrine differentiation in this case, despite its location in the breast, an organ rich in specialized apocrine (lactiferous) glands. To our knowledge, this represents the first reported case of syringocystadenoma papilliferum of the male breast. We present the clinical and pathologic features of this unusual case and a review of the literature.