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.