ENDOTHELIAL-CELL MARKERS CD31, CD34, AND BNH9 ANTIBODY TO H-ANTIGEN AND Y-ANTIGEN - EVALUATION OF THEIR SPECIFICITY AND SENSITIVITY IN THE DIAGNOSIS OF VASCULAR TUMORS AND COMPARISON WITH VON-WILLEBRAND-FACTOR

Sixty vascular tumors including 23 angiosarcomas, 300 nonvascular tumo rs, and selected normal tissues were immunohistochemically evaluated w ith antibodies to CD31, CD34, and von Willebrand factor (vWF), and mon oclonal antibody BNH9, to test the sensitivity and specificity of thes e markers in the identification of endothelial cells and vascular tumo rs. Formaldehyde-fixed paraffin-embedded tissues and avidin biotin com plex immunostaining were used. All markers labeled normal vascular and lymphatic endothelial cells approximately equally with the exception of CD34 which showed inconsistent expression within the lymphatics. In addition, antibody to CD31 reacted with platelets and megakaryocytes, CD34 with fibroblasts and aortic smooth muscle cells, and BNH9 with m any epithelial cells including squamous and gastrointestinal epithelia . Antibody to vWF often showed significant stromal background staining which made the staining occasionally uninterpretable. Benign vascular tumors showed rather uniform staining with all antibodies. However, a ngiosarcomas were heterogeneous; CD31 was positive in 21/27, CD34 in 2 5/27 cases, BNH9 in 22/25, and vWF in 18/27 cases. Epithelioid hemangi oendotheliomas showed consistent labeling for vWF, but were inconsiste ntly labeled with antibodies to the other markers. Kaposi's sarcoma wa s positive for both CD31 and CD34. In addition, antibody to CD34 label ed the tumor cells in hemangiopericytoma, cerebellar hemangioblastoma, meningioma, most epithelioid sarcomas, dermatofibrosarcomas, and in a few other sarcomas. CD31, in turn, was not found in sarcomas other th an angiosarcomas, but labeled weakly occasional carcinomas and mesothe liomas. Many adenocarcinomas and the glandular component of synovial s arcoma were BNH9 positive. We conclude that CD31 is the most specific endothelial cell marker. CD34 is present widely in normal mesenchymal tissues and nonvascular tumors besides angiosarcomas, and BNH9 reactiv ity in a variety of carcinomas. The widespread presence of vWF as a se rum component may render the immunostains uninterpretable in some case s. For the diagnosis of angiosarcomas we recommend simultaneous use of several markers because these tumors show heterogenous expression of the endothelial cell antigens.