Case Report: Cardiac metastasis from urothelial carcinoma with predominant squamous differentiation in a young woman: first reported case treated with enfortumab vedotin plus pembrolizumab.

Cardiac metastases from urothelial carcinoma (UC) are rare and have a poor prognosis. A 36-year-old woman presented with de novo metastatic muscle-invasive bladder cancer, bulky retroperitoneal lymphadenopathy, and a large right ventricular mass nearly obliterating the cavity and extending to the pulmonary artery. Because of impending right ventricular outflow tract obstruction, urgent surgical debulking was performed; a friable tumor encasing the tricuspid valve filled the right ventricle, valve preservation was not feasible, and postoperative pacing was required. Transurethral resection of the bladder tumor showed high-grade UC with predominant (80%) squamous differentiation, while the cardiac lesion demonstrated a pure squamous phenotype with immunohistochemistry supporting urothelial origin. Given a very high tumor burden and postoperative cisplatin ineligibility, first-line enfortumab vedotin plus pembrolizumab was initiated, but the patient rapidly deteriorated with early radiologic progression and died ~8 weeks after diagnosis. This case illustrates the aggressive course of squamous-dominant metastatic UC with intracardiac involvement, the therapeutic trade-off of urgent cardiac surgery, and the limited evidence for enfortumab vedotin-based regimens in squamous-predominant disease.