Masson's intravascular vegetant hemangioendothelioma.

Eleven cases of Masson's hemangioendothelioma are reported. This benign condition must be distinguished histologically from numerous malignant endothelial lesions. Two different papillary structures were observed; one defined as "inflammatory papilla" was constantly associated with a thrombus; the other, defined as "fibrous papilla" was observed in 4 cases where no thrombus could be found. It is postulated that the inflammatory papillae are an exuberant endothelial growth during the normal organisation of a thrombus; fibrous papillae, it is suggested, might be reactive to blood or lymph stasis.