We report a 47 year-old woman with a unique breast cancer coexisting with florid papillomatosis (FP) of the left nipple. The diseased nipple was enlarged and reddened. There was an area of erosion on the surface. Incisional biopsy revealed FP of the nipple. Under the nipple, there was an elastic hard tumor with an unclear border and irregular surface. Aspiration biopsy cytology of the tumor revealed carcinoma. Modified radical mastectomy was performed. Histological examination showed that the superior portion of the tumor was FP, and most of the tumor in and under the nipple was breast cancer. To the best of our knowledge, only 16 cases of FP of the nipple have been reported in the Japanese literature. FP of the nipple coexisting with carcinoma in the same nipple has never been reported. This is thought to be the first case in Japan of mammary carcinoma coexisting with FP in the same nipple.