Malignant hemangioendothelioma of the thyroid. Its immunohistochemical discrimination from undifferentiated thyroid carcinoma.

Eighteen cases of malignant hemangioendothelioma (MHE) of the thyroid and 16 cases of undifferentiated thyroid carcinoma were investigated immunohistochemically with antibodies against endothelial cell specific markers (factor VIII-related antigen, BMA 120, blood group isoantigens, Ulex europaeus agglutinin I), thyroglobulin, and the intermediate filament proteins vimentin and cytokeratin. All MHE were positive for factor VIII-related antigen and vimentin, in 14 of 18 cases for BMA 120, and in 9 of 18 cases for U. europaeus. All other markers were negative in MHE. Endothelial cell specific markers were commonly negative in undifferentiated carcinomas with one exception (one case was moderately positive for U. europaeus). Twelve of 16 undifferentiated carcinomas showed vimentin positivity, and 8 of 16 showed cytokeratin positivity. Four cases showed a vimentin/cytokeratin coexpression. It is concluded that the endothelial origin of MHE can be shown by certain endothelial cell markers in almost all cases.