Seminal Vesicle Leiomyoma Mimicking Extra-prostatic Extension of Prostatic Adenocarcinoma

Leiomyomas are common smooth muscle neoplasms; however, leiomyomas of the seminal vesicles are extremely rare. We report a case of seminal vesicle leiomyoma in a 55-year-old African American male who underwent robot assisted laparoscopic prostatectomy (RALP) for Gleason 8 (4 + 4) adenocarcinoma. An incidental nodule arising from the left seminal vesicle was discovered during surgery, complicating the surgical dissection and suggesting extra-prostatic extension. The histologic findings in this case raised the possibility that this seminal vesicle leiomyoma may have arisen from a remnant of the mid-portion of the Müllerian duct; however, a thorough immunohistochemical (IHC) workup disproved this theory.