Melanoma Mimicker: Pigmented Mammary Paget Disease in a Man

Male breast cancer comprises less than 1% of all breast cancer cases. Mammary Paget disease (MPD) represents a subset of breast cancer that presents with skin changes of the nipple and areola, and is frequently misdiagnosed clinically due to similarities with other disease states, leading to an average delay in diagnosis of 1 month to 2 years. Pigmented mammary Paget disease (PMPD) is an uncommon variant of MPD that clinically and histologically resembles malignant melanoma. Due to variable immunohistochemical staining patterns, analysis can be challenging and often requires interpretation of panels for accurate diagnosis. We present a rare case of PMPD in a male, originally diagnosed both clinically and histologically as malignant melanoma, to highlight the diagnostic challenges that this entity presents, and to review staining patterns which may be useful in its diagnosis.