Intravascular papillary endothelial hyperplasia of renal vein: report of 2 cases.

Intravascular papillary endothelial hyperplasia is a benign intravascular process thought to arise from an organizing thrombus. The lesion may present clinically as an abnormal mass and, depending on the location, may be confused with benign or malignant neoplasms. It has been described in a variety of locations. Involvement of the renal vein by papillary endothelial hyperplasia is extremely rare, with only 4 cases reported in the literature. We describe 2 additional cases. In both cases, the radiologic examination revealed a well-circumscribed mass in the hilar region of the kidney, which was considered to be a renal neoplasm. Nephrectomy specimen in each case revealed characteristic features of intravascular papillary endothelial hyperplasia. It is suggested that intravascular papillary endothelial hyperplasia should be included in the differential diagnosis of a hilar renal mass.