A unique surgical case of giant invasive intracystic carcinoma of the male breast focusing on cytological findings.

A 60-year-old male presented with a history of a relatively hard and cystic right chest mass that had gradually increased in size, with subsequent skin erosion, exudate and hemorrhage. The cytologic specimens from a cyst fluid contained a large number of sheet-like or papillary clusters of atypical cuboidal to columnar epithelial cells with loss of myoepithelial components, in a severely inflammatory background with scattered siderophages. We first interpreted it as a carcinoma, but could not completely exclude out the possibilities of benign. Tumor extirpation was performed, and a gross examination of the neoplasm revealed a giant, cystic and partly solid papillary-projected tumor lesion, with a gray-whitish cut surface, associated focally with skin invasion, measuring approximately 9 × 7 cm with a 6 × 4 cm solid area in diameter. On a microscopic examination, solid parts of the tumor were predominantly composed of the intracystic proliferation of mildly atypical epithelial cells with absence of two-cell patterns in a papillary or papillotubular growth fashion, only partly involving the dermis to epidermis. Immunohistochemistry showed that the carcinoma cells were specifically positive for estrogen and progesterone receptors, whereas negative for p63, S-100 protein and several neuroendocrine markers. Therefore, we finally made a diagnosis of invasive intracystic carcinoma of the male breast. We should be aware that owing to its characteristic cytological features, cytopathologists might be able to make a correct diagnosis of that, based on multiple and adequate samplings, even though a core biopsy would be the absolute minimum assessment.