Urothelial carcinoma of the bladder with prostatic stromal invasion and early postoperative bone metastases: a case report.

BACKGROUND: Prostatic involvement by bladder urothelial carcinoma is uncommon, and prostatic stromal invasion usually indicates aggressive tumor biology and poor prognosis. Such patients may present with prostatic enlargement or a mass at the bladder neck-prostate junction, while serum prostate-specific antigen (PSA) may remain within the normal range. This diagnostic overlap may lead to clinical confusion with benign prostatic hyperplasia or primary prostatic tumors. CASE PRESENTATION: A 54-year-old man was admitted with urinary frequency, urgency, dysuria, and intermittent gross hematuria. Serum PSA on admission was 2.1 ng/mL. Imaging suggested a mass at the bladder neck-prostate junction with an indistinct boundary between the bladder and prostate. After transurethral resection of a bladder lesion, pathology and immunohistochemistry indicated high-grade invasive urothelial carcinoma. Tumor cells expressed CK20, GATA3, and p63, partially expressed CK7 and Uroplakin III, and were negative for PSA and NKX3.1. The patient subsequently underwent radical cystectomy, ileal conduit urinary diversion, and pelvic lymph-node dissection. Postoperative pathology revealed high-grade bladder urothelial carcinoma with invasion of the prostatic stroma and capsule, staged as pT4aN0M0, with lymphovascular invasion, perineural invasion, and a positive prostatic urethral margin. PD-L1 expression was low (TPS <1%, IC <1%), and HER2 was negative. Because no neoadjuvant systemic therapy had been given and the final pathology showed pT4a disease with a positive margin, adjuvant systemic therapy was recommended and initiated. The patient received only approximately one week of platinum-based chemotherapy plus immunotherapy; treatment was discontinued because of poor tolerance and substantial financial burden. Three months after surgery, the patient developed low back pain. Whole-body bone scintigraphy and SPECT/CT demonstrated multiple bone metastases involving the L2 and L4 vertebrae and posterior elements, bilateral iliac bones, the left acetabular rim, and the right inferior pubic ramus. He subsequently received denosumab combined with conformal intensity-modulated radiotherapy to vertebral metastatic lesions. CONCLUSION: This case highlights that a normal PSA level does not exclude prostatic involvement by bladder-derived urothelial carcinoma. For patients with bladder neck or prostatic masses, especially those with normal PSA but imaging evidence of bladder-prostate junction involvement, an immunohistochemical panel including GATA3, CK7, CK20, p63, Uroplakin III, PSA, and NKX3.1 should be used early for differential diagnosis. Prostatic stromal invasion combined with lymphovascular invasion, perineural invasion, and a positive surgical margin may indicate highly aggressive disease and an increased risk of early distant metastasis, requiring intensified postoperative risk assessment, systemic treatment decision-making, and close follow-up.