The presence of supernumerary nipples, known as polythelia, is the most common presentation of accessory breast tissue. It is usually considered to be a benign congenital anomaly. However, polythelia may warrant attention for more than mere cosmetic concern because supernumerary nipples have been shown to be associated with an increased risk of genitourinary malignancies. We describe a 53-year-old man with an accessory nipple on the left chest who presented with stage IIA testicular seminoma at the age of 47. Published reports of patients with polythelia and genitourinary malignancies, as well as other neoplasms, are reviewed. Because patients with accessory nipples have a predisposition to develop visceral cancers, polythelia should be considered as a genodermatosis with malignant potential.