Castleman's tumor with retroperitoneal location: a malignant-appearing benign tumor.

A case of a large retroperitoneal tumor in the pararenal region is presented. The tumor had an initial appearance of a malignant neoplasm both radiographically and at operation but histopathologically it turned out to be a rare benign tumor, Castleman's disease. Based on the benign nature of this lymphoid tumor extensive surgical procedures should be avoided as limited excision of the tumor appears to have been curative in all the patients reported in the literature.