Embryonal Rhabdomyosarcoma of the Prostate in a Young Adult

Embryonal rhabdomyosarcoma (ERMS) is a primitive and aggressive soft tissue tumor that arises from premature mesenchymal cells and accounts for less than 1% of prostate malignancies. We present the case of a 26-year-old Filipino male who initially sought consultation and work-up for acute urinary retention. Although his prostate-specific antigen (PSA) level was normal, a kidney-ureter-bladder (KUB) ultrasound revealed an incidental finding of an enlarged prostate gland. Subsequent imaging tests (MRI and CT) identified a large, partially exophytic mass on the prostate with intravesical extension. The patient underwent a biopsy via transurethral resection at another institution, which yielded findings of a poorly differentiated carcinoma, primarily suggesting prostatic adenocarcinoma with a Gleason score of 10 (5+5). A request for slide review was submitted to our institution, and subsequent immunohistochemistry (IHC) studies-highlighting the tumor's immunoreactivity to myogenin and desmin-confirmed the diagnosis of ERMS. In this report, we discuss the clinical features, pathogenesis, treatment, diagnosis, and prognosis of this rare prostate tumor.