Abstract
Male mammary Paget's disease (MPD) is extremely rare. Furthermore, MPD with invasion downward into the dermis of the male nipple has been reported rarely. A 56-year-old Japanese man presented with a lump and eczema in the right nipple-areola area. Ultrasonography revealed only a cystic lesion below the right areola. With a diagnosis of MPD with invasion into the dermis associated with ductal carcinoma in situ, mastectomy and sentinel lymph node biopsy were performed. MPD with dermal invasion is extremely rare, and only one male case has been reported in the English literature; therefore, the current case is the second case of male MPD with dermal invasion.