Adenoma of the nipple with carcinomatous development. A tumour of the nipple of a 56-year-old woman had the characteristics of an adenoma of the nipple and was considered benign in spite of small areas of cellular polymorphism. The patient died five weeks later and at necropsy tumour metastases were found in lymph nodes in the right axilla, similar to the nipple tumour. Other metastases in lymph nodes, liver, left kidney, spleen and spinal column were less differentiated but were apparently secondaries of the nipple tumour. No other primary tumour was found at autopsy. Adenoma of the nipple is generally considered a benign tumour, and this case is the first example of malignant change and general spread.