Reactive angioendotheliomatosis or intravascular histiocytosis? An immunohistochemical and ultrastructural study in two cases of intravascular histiocytic cell proliferation

Two elderly women with complex medical histories presented with erythematou s patches, in one case involving the face and forearms, and in the other bo th elbows. Punch biopsies from both patients revealed intravascular prolife rations of medium-sized and large cells with luminal occlusion typical of a ngioendotheliomatosis. Immunostaining did not show either lymphocytic or en dothelial cell antigens but was consistent with a histiocytic differentiati on of the intravascular cells in both cases, and was further substantiated by ultrastructural examination in one case, One patient received a course o f cyclophosphamide therapy over 15 days. Skin lesions faded but did not dis appear. The patient died 10 months later from cardiac and renal failure, wh ich was most probably unrelated to the skin lesions. In the other case, les ions diminished but did not entirely resolve with treatment with low doses of oral prednisone. Angioendotheliomatosis can be divided into a malignant variant, which is an angiotropic lymphoma mostly of B-cell phenotype, and a benign, reactive variant, which is characterized by a proliferation of cel ls expressing endothelial cell markers, Only one case of angioendotheliomat osis with cells of histiocytic differentiation has been published previousl y under the name of intravascular histiocytosis, Our cases are very similar to the latter. The question arises as to whether intravascular histiocytic cell proliferation is a neoplastic proliferation of histiocytes or an earl y stage of classic reactive angioendotheliomatosis representing the residua l cells associated with organization of microthrombi, which will be later f ollowed by endothelial cell proliferation.