Abstract
Upper tract transitional cell carcinoma poses diagnostic challenges due to its prevalence and diverse clinical presentations. This case report describes the incidental discovery of high-grade transitional cell carcinoma during the management of a 48-year-old male with ischemic heart disease and an asymptomatic right renal stone. During flexible ureteroscopy for stone removal, papillary lesions were identified within a calyceal diverticulum and confirmed as high-grade transitional cell carcinoma. The unique anatomy of the calyceal diverticulum, characterized by its restricted wall thickness, may predispose the tumor to early metastasis. Additionally, there is a concern about potential iatrogenic dissemination of tumor cells to the bladder during the ureteroscopic procedure. This case highlights the diagnostic complexities associated with upper tract transitional cell carcinoma in rare anatomical locations and emphasizes the need for careful consideration of both procedural factors and anatomical features to manage the risk of metastasis and tumor dissemination effectively.