A case of intravascular papillary endothelial hyperplasia (Masson's tumor) arising from renal sinus.

A 55-year-old woman had a right renal tumor incidentally diagnosed by ultrasonography. CT revealed a perirenal low density mass 3 cm in diameter. Dynamic CT showed peripheral enhancement of the tumor in early phase and internal homogeneous enhancement in delayed phase. Since hemangioma was considered most likely, we performed tumor resection and spared the right kidney. The tumor was supplied by the superior ureteral artery from the right main renal artery which was considered to be derived from the renal sinus. The tumor was diagnosed as intravascular papillary endothelial hyperplasia (Masson's tumor). This is the first report of intravascular papillary endothelial hyperplasia existing in the perirenal space. Although preoperative diagnosis of intravascular papillary endothelial hyperplasia is difficult, intra-operative pathology and kidney-sparing treatment should be considered in such a case.