Aberrant mammary tissue and nephrourinary malignancy.

Polythelia (supernumerary nipple) provides a clue to congenital and hereditary malformations of the kidney and the urinary collecting system. It is also regarded as a cutaneous paraneoplastic marker because of the significant association with urogenital malignancies. A 38-year-old man with sporadic left supernumerary nipple without evidence of ear, facies, or gonadal defects or lateral displacement of the nipples was routinely examined for the presence of renal anomalies. Investigation revealed left polycystic kidney disease with adenocarcinoma in the upper pole. The nephrocutaneous defects and renal malignancy showed a peculiar ipsilaterality. The overlap between polythelia, polycystic kidney disease with adenocarcinoma in the upper pole. The nephrocutaneous defects and renal malignancy showed a peculiar ipsilaterality. The overlap between polythelia, polycystic kidney, and renal adenocarcinoma may provide a further clue to the embryonal origin of this cancer.