Papillary endothelial proliferation in cystic lymphangiomas. A lymphatic vessel counterpart of Masson's vegetant intravascular hemangioendothelioma.

Papillary endothelial proliferation similar to that of Masson's "vegetant intravascular hemangioendothelioma" of the blood vessels was observed in two cases of cystic lymphangiomas. They are believed to be the lymphatic vessel counterpart of Masson's entity. Twenty-five other specimens of various lymphangiomas examined (18 patients) did not contain the same change. As was emphasized previously for Masson's lesions, lymphangiomas containing similar endothelial changes should also not be mistaken for malignant vascular tumors, since in these two cases, no unusual clinical course supervened. Although the histogenesis of the lesion as proposed by Masson has been disputed, both primary and secondary endothelial proliferation seem to remain possible in the formation of these lesions.