A case of an adenoma of the nipple was reported. A 44-year old woman presented with bloody nipple discharge. No breast mass or skin involvement was observed. Ultrasonography revealed low echoic dilated duct and high echogenic mass inside. Cytological examination revealed a cluster of cells showing papillary growth. Microdochectomy was performed and histological examination revealed the mass being adenoma of the nipple. Clinical importance to avoid over-surgery and co-operation of surgeons and pathologists were discussed.