A report of renal cell carcinoma in a horseshoe kidney

: A case of renal cell carcinoma associated with horseshoe kidney is reported. The patient was a 67 years old man with the chief complaints of dull pain of right upper abdomen. Ultrasonography (US) revealed horseshoe kidney and abnormal mass sign at the right isthmus of the kidney. By the computed tomography (CT) and angiography, renal cell carcinoma associated with horseshoe kidney was diagnosed. Only 18 cases of this rare disease have been reported in Japan. The diagnostic procedures are discussed and the usefulness of selective arteriography of the isthmus is emphasized, as the presentation of vascular anatomy is of great value for diagnosis, surgical treatment and preoperative arterial embolization.