A Pelvic “Black Pearl”: Acute Urinary Retention due to Pelvic Pleomorphic Rhabdomyosarcoma

Abstract

Acute urinary retention (AUR) in elderly men is most commonly attributed to benign prostatic hyperplasia or urethral pathology. The coexistence of lower urinary tract symptoms (LUTSs), fever, and a tender mass on digital rectal examination typically directs the clinician toward a diagnosis of acute prostatitis or prostatic abscess. We report a rare and diagnostically challenging case of a 68-year-old man presenting with LUTS, fever, and AUR, initially suspected to have a benign pelvic schwannoma based on magnetic resonance imaging. Surgical exploration revealed a large pelvic mass densely adherent to the bladder and rectum. Histopathological examination demonstrated a high-grade pleomorphic rhabdomyosarcoma with extensive necrosis, rhabdoid morphology, and the unusual presence of Touton-type giant cells. This case highlights a rare nonurological cause of urinary retention, the radiological mimicry of benign neurogenic tumors by pelvic sarcomas, and the emerging spectrum of inflammatory rhabdomyoblastic tumors. Early suspicion, preoperative biopsy, and multidisciplinary management are essential to optimize outcomes in such aggressive malignancies.