Urothelial Carcinoma within a Calyceal Diverticulum Difficult to Distinguish from Cystic Renal Cell Carcinoma

: A 64-year-old man visited our hospital because of right renal cyst and microscopic hematuria which was found in a medical checkup. Contrast computed tomography (CT) and contrast magnetic resonance imaging (MRI) suggested cystic renal cell carcinoma. A laparoscopic nephrectomy was performed, and the surgical specimens showed urothelial carcinoma within the calyceal diverticulum. At a later date, ureterectomy was performed. The surgical specimens had no malignant findings. There has been no recurrence. To our knowledge only 10 cases of urothelial carcinoma within the calyceal diverticulum have beenreported inJapan. A few cases have beenreported overseas.