RESUMEN
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. The main significance of intravascular papillary endothelial hyperplasia is its clinical and histological resemblance to soft-tissue sarcoma and possible misinterpretation as such. A case of intravascular papillary endothelial hyperplasia clinically diagnosed and treated as a low-grade angiosarcoma, in a 60-year-old man, presenting with a mass in the left thigh, is reported.