Reactive and malignant "angioendotheliomatosis": a discriminant clinicopathological study

In order to determine whether or not phenotypic differences existed between reactive angioendotheliomatosis (RAE) and malignant angioendotheliomatosis (MAE), we studied the histological and immunohistochemical features of 4 and 8 cases of these lesions, respectively. Antibodies to leukocyte common antigen (LCA), specialized B- and T-lymphocytic determinants, Factor VIII-related antigen (FVIIIRAG), blood group isoantigens A, B, and H (BGI), epithelial antigens, vimentin, and actin; and Ulex europaeus I lectin (UEL) were utilized. Cutaneous lesions in all cases of MAE were part of a disseminated, fatal, intravascular cellular proliferation, with highly atypical cytological features. Because one of the patients in this group had cardiac valvular vegetations at autopsy, this case had been reported previously as representative of RAE. However, the latter example, as well as all others of MAE, stained strongly for LCA, B-cell antigens, and vimentin in tumor cells. FVIIIRAG was seen focally in 6 cases, in cells entrapped in platelet-fibrin thrombi; however, UEL binding and reactivity for BGI were uniformly absent. Conversely, RAE was typified by a cytologically-bland intravascular proliferation, with actin-positive, perivascular, pericytic cuffs. All 4 patients in this group had cutaneous involvement only, and the lesions tended to be self-resolving. One had pulmonary tuberculosis, but evidence for an underlying infection was absent in the remainder of RAE cases. Immunohistologically, RAE displayed universal reactivity for FVIII-RAG, BGI, UEL, and vimentin, and negativity for LCA in intravascular cells. Neither MAE nor RAE showed the presence of epithelial determinants. These data indicate that MAE and RAE are clinicopathologically distinct entities, showing lymphoid and endothelial features, respectively. Because of the phenotypic properties of the former condition, it would appear advisable to substitute the term "intravascular lymphomatosis" for "malignant angioendotheliomatosis".