Cystic endometriosis of the epididymis

Endometriosis of the male genitourinary tract is an exceedingly rare entity, with only 6 cases reported to date involving the bladder, prostate, lower abdominal wall, and paratesticular region.We present what we believe to be the first case of cystic endometriosis of the epididymis in a 27-year-old man with scrotal pain, describe its pathologic and immunohistochemical features, and discuss its pathogenesis.