Apocrine mammary carcinoma. A clinicopathologic study of 72 cases. Apocrine carcinoma (AC) is an uncommon, poorly characterized type of breast tumor. In this review, 55 patients with intraductal (ID) AC and 17 patients with infiltrating (IF) AC were analyzed retrospectively to define the histologic features and clinical course of this neoplasm. Recurrences in the breast occurred in 3 of 20 ID-AC patients treated by biopsy alone, but not in the 2 patients who received local radiation therapy after biopsy. One patient with ID-AC had axillary metastases at the time of treatment by mastectomy and died of disease five years later. The remaining patients with ID-AC treated by mastectomy have remained disease free. One of the three patients with IF-AC treated by biopsy alone died of disease, and one of two patients with IF-AC treated by biopsy and radiotherapy was alive with carcinoma. Twelve patients with IF-AC were treated by mastectomy. Ten of them were recurrence free at the time of last observation. More than one-third of the cases of ID-AC and IF-AC were detected by mammography alone. Survival analysis of IF-AC cases compared with nonapocrine duct carcinoma cases matched for stage revealed no statistical difference in estimated recurrence-free survival or estimated survival probability. AC is a distinct morphologic entity with a natural history similar to that of nonapocrine ductal carcinoma. 