Intravascular papillary endothelial hyperplasia (Masson's hemangioma) presenting as a soft-tissue sarcoma.

Intravascular papillary endothelial hyperplasia (Masson's hemangioma) is an unusual benign, non-neoplastic, vascular lesion characterized histologically by papillary fronds lined by proliferating endothelium. It may appear as a primary or pure form developing in a distended vessel, or it can be associated with hemangiomas, pyogenic granulomas, or lymphagiomas. Nearly all lesions are intimately associated with a thrombus in various stages of organization.