Case Report: Cardiac metastasis of sarcomatoid urothelial carcinoma

Sarcomatoid urothelial carcinoma (SUC) is a rare, highly aggressive subtype of urothelial carcinoma (UC) accounting for fewer than 1%-2% of all urothelial malignancies. It is characterized by biphasic histology, a dismal prognosis, resistance to conventional chemotherapy, and a propensity for distant metastasis. Clinically confirmed cardiac metastasis from UC is exceedingly rare, with only sporadic cases documented worldwide.

We report a 55-year-old woman who presented with right-sided flank pain and gross hematuria. Percutaneous renal biopsy confirmed right renal pelvis SUC with approximately 85% sarcomatoid component. The patient underwent palliative robot-assisted laparoscopic nephroureterectomy; final pathological staging was pT3N1M1 (Stage IV). Approximately two months postoperatively, imaging confirmed multifocal metastases involving the lungs, pleura, liver, and lymph nodes, and first-line chemo-immunotherapy was initiated with gemcitabine plus carboplatin plus nivolumab. Carboplatin was substituted for cisplatin because the patient was deemed cisplatin-ineligible owing to renal insufficiency, following a modified CheckMate 901 framework. After one cycle, grade IV myelosuppression (platelet nadir 28 × 10⁹/L) necessitated permanent discontinuation of cytotoxic agents. During myelosuppression recovery, the patient developed palpitations; echocardiography revealed a large, broad-based right ventricular (RV) mass (50 × 41 mm). Treatment was revised to tislelizumab monotherapy (200 mg, every three weeks [q3w]). Serial echocardiographic follow-up documented progressive RV mass regression from 50 × 41 mm to 22 × 32 mm and ultimately to 11 × 14 mm, with stable systemic disease throughout.

To our knowledge, this is the first documented case of isolated RV metastasis from right renal pelvis SUC achieving an objective response to anti-PD-1 immunotherapy. The sustained imaging regression under tislelizumab monotherapy strongly suggests-but does not definitively confirm-a metastatic etiology. For patients with high PD-L1-expressing SUC and cardiac metastasis who are intolerant of combined chemo-immunotherapy regimens, immune checkpoint inhibitor monotherapy may represent a feasible and well-tolerated treatment strategy.