Intravascular papillary endothelial hyperplasia (Masson tumor) mimicking a sarcoma and developing from an arteriovenous hemodialysis fistula.

Intravascular papillary endothelial hyperplasia (IPEH), also known as Masson's tumor, is a rare nonneoplastic vascular lesion caused by the abnormal proliferation of endothelial cells. Clinically and radiologically, IPEH presents as a soft tissue mass that may simulate and be mistaken for a sarcomatous tumor. There have been reports of this entity involving the skin or subcutaneous tissues in normal blood vessels and vascular malformations. Herein, we present the first reported case of Masson's tumor arising from an arteriovenous hemodialysis fistula. We emphasize the imaging features of this lesion and briefly discuss its pathophysiology.