Prostatic specific antigen-positive adenocarcinoma arising from a stromal tumor of uncertain malignant potential in the Müllerian cyst of the male genital tract: A case report

Abstract We report a case of prostatic-specific antigen (PSA)-positive adenocarcinoma arising from a stromal tumor of uncertain malignant potential (STUMP) in the Mullerian cyst of the male genital tract. The patient was a 47-year-old man with an elevated serum PSA level (16.4 ng/mL) that was detected during a medical check-up. Gross examination of the prostatectomy specimen revealed a tumor 3 cm in diameter between the seminal vesicles on both sides and the prostate; the tumor did not invade the prostate. On microscopic examination, a STUMP with a phyllodes pattern was observed entirely within the Mullerian cyst, with an acinar adenocarcinoma component invading the STUMP stroma. The epithelium of the Mullerian cyst wall showed both PAX8+ Mullerian and PSA+ prostatic phenotypes. Both the epithelium of the STUMP and the adenocarcinoma component showed PAX8-, NKX3.1+, and PSA+ prostatic phenotypes. The epithelial component of the STUMP and the adenocarcinoma that showed prostatic phenotypes were likely derived from the Mullerian cyst epithelium, which had not only Mullerian but also prostatic phenotypes.