Fifteen cases of papillary adenoma (florid papillomatosis, erosive adenomatosis) of the nipple were compared with forty examples of syringadenoma papilliferum, twenty-four of hidradenoma papilliferum, and one hundred of breast carcinoma metastatic to skin. Clinically, papillary adenoma of the nipple typically occurred in a female patient as an erosion, ulceration, or mass that was sometimes accompanied by serous or bloody discharge from the nipple and was frequently misdiagnosed as Paget's disease. Histologically, there was usually a papillary and adenomatous growth in the corium that connected with the surface and showed a lining of apocrine type secretory epithelium, a sometimes plasmacytic stroma, and horn cysts in the upper corium. Papillary adenoma of the nipple is often histologically misinterpreted as syringadenoma papilliferum, hidradenoma papilliferum, or low-grade adenocarcinoma, but it has received almost no attention in the dermatology literature.