[A case of accessory spleen presenting as retroperitoneal tumor].

We report the 13th case of accessory spleen in the retroperitoneum in the world literature. A 53-year-old man visited our hospital complaining of lassitude. Laboratory studies revealed significant anemia. Several imaging studies revealed a large retroperitoneal tumor (70 x 63 x 48 mm) in the medial aspect of the lower pole of the left kidney. The tumor was supplied arterially from the first and second lumbar arteries. Since the tumor adhered tightly to the left kidney, the kidney was resected as well as the tumor. The tumor was very hemorrhagic. On histological examination, the tumor exhibited a structure typical of splenic tissue. The retroperitoneal accessory spleen is very rare, and the literature on it is reviewed here.