De Novo Primary Squamous Cell Carcinoma of the Prostate: Substantial Tumor Regression After Definitive Radiotherapy in a Medically Inoperable Patient.

Primary squamous cell carcinoma (SCC) of the prostate is a rare and biologically aggressive malignancy lacking a standardized management strategy. De novo primary SCC arising without prior androgen deprivation therapy or radiotherapy is uncommon and presents significant diagnostic and therapeutic challenges. We present the clinical presentation, diagnostic evaluation, treatment strategy, and early therapeutic response of de novo primary SCC of the prostate in a 56-year-old male with end-stage renal disease on maintenance hemodialysis. The patient presented with gross hematuria and a bulky prostate mass invading the bladder with bilateral pelvic lymphadenopathy despite low prostate-specific antigen (PSA) levels. Histopathological and immunohistochemical analyses confirmed pure SCC, staged as cT4N1M0. Because systemic chemotherapy was contraindicated and surgery was not feasible, definitive whole-pelvis radiotherapy with a simultaneous integrated boost was administered. Marked tumor regression was observed one month after treatment. Subsequent imaging demonstrated extensive tumor necrosis with fistulous communication in the context of locally invasive disease. Because long-term oncologic durability could not be assessed owing to non-oncologic clinical deterioration, these findings suggest that definitive radiotherapy may provide meaningful locoregional tumor control in selected medically inoperable patients with de novo prostatic SCC.