Masson's intravascular papillary endothelial hyperplasia mimicking Stewart-Treves syndrome: report of a case.

Masson's intravascular papillary endothelial hyperplasia, also called Masson's pseudoangiosarcoma, represents a benign vascular proliferation, presently considered as a peculiar histopathologic reaction pattern of the endothelium to diverse stimuli. Differentiation from angiosarcoma represents the main diagnostic concern. We report a case of Masson's intravascular papillary endothelial hyperplasia presenting in a 55-year-old woman with ipsilateral lymphedema secondary to surgery and radiation therapy for breast carcinoma. The diagnosis was intravascular papillary endothelial hyperplasia. This is the first description of Masson's pseudoangiosarcoma in this clinical context, to our knowledge. We believe it represents a peculiar morphologic pattern of endothelium proliferation secondary to venous stasis and thrombosis due to lymphedema.