To encounter an apocrine carcinoma of the breast is very rare. We have experienced, however, 10 cases of an apocrine carcinoma (0.65%) among 1541 primary breast carcinoma cases. The mean age of the patients was 58.1 years, and the tumor size on palpation ranged from 1.1 to 6.0 cm (mean 3.5 cm). A lymph node metastasis was seen in 5 cases. While one patient determined as being in stage III b of the disease died of the cancer approximately 5 months after surgery, all of other patients are still alive. The prognosis of this type of disease appears to be better than that of a common invasive ductal carcinoma. Thirty-four cases of an apocrine carcinoma have been found in the Japanese literature, this number including our 10 cases. Discussed are the clinicopathological features and the histogenesis of this type of cancer.