Squamous Cell Carcinoma Arising From a Renal Calyceal Diverticulum

Calyceal diverticulum is an eventration of the upper collecting system within the renal parenchyma. This nonsecretory outpouching is lined by transitional epithelium and communicates with the main collecting system via a narrow channel. Tumor growth arising from a calyceal diverticulum is rare, and primary squamous cell carcinoma arising from a calyceal diverticulum has never been described in literature. Herein, we report a case of primary squamous cell carcinoma arising from a calyceal diverticulum and present initial imaging of a benign-appearing cystic lesion.