Supplementary Material for: Cardiac Metastasis in Upper Tract Urothelial Carcinoma with Squamous Differentiation: A Case Report

Introduction: Upper tract urothelial carcinoma (UTUC), accounting for 5–10% of urothelial malignancies, rarely metastasizes to distant sites such as the heart. Case Presentation: This report describes a rare case of cardiac metastasis in a 62-year-old male with a complex history of recurrent urothelial carcinoma. Initially diagnosed with bladder cancer in 1999, the patient underwent multiple resections and intravesical therapies, followed by cystectomy in 2012 due to refractory anaplastic tumors. A decade later, he developed right-sided hydronephrosis and hematuria, prompting nephroureterectomy, which revealed papillary urothelial carcinoma with squamous differentiation (pT3pNxMx). Despite aggressive local management, cardiac metastasis involving the right ventricular myocardium was identified in 2023. Systemic chemotherapy yielded minimal response, and the patient eventually succumbed to progressive cardiac failure. Conclusion: Squamous differentiation in urothelial carcinoma predicts aggressive, treatment-resistant behavior. Delayed post-cystectomy recurrence supports the concept of field cancerization and necessitates lifelong surveillance. Rare cardiac metastasis confirms the hematogenous spread potential and underscores the need for improved adjuvant therapies.