The patient was a 16-year-old male who visited our hospital with the chief complaint of microhematuria. Computed tomography revealed left hydronephrosis, renal stones and left renal tumor. Needle biopsy was performed under ultrasonography. The histological diagnosis was adenocarcinoma and left radical nephrectomy was performed. The histological diagnosis was mucinous adenocarcinoma of the renal pelvis. Postoperative chemotherapy was not given. The patient has had neither recurrence nor metastasis for 1 year following surgery. This is the 92nd reported case in the literature.