Angiomatoid carcinoma and 'angiosarcoma' of the thyroid gland. A spectrum of endothelial differentiation.

The existence of angiosarcoma of the thyroid gland and its relation to angiomatoid carcinoma have been debated. The authors reviewed eight angiomatoid thyroid neoplasms. Controls consisted of six sarcomatoid thyroid carcinomas without angiomatoid features and an angiosarcoma metastatic to the thyroid gland. All eight angiomatoid neoplasms consisted of epithelioid cells with prominent eosinophilic cytoplasm lining vascularlike spaces. All eight expressed vimentin. Four tumors were predominantly angiosarcomalike neoplasms, based on staining for factor VIII-related antigen (three of four), CD31 (four of four), CD34 (one of four), and Ulex europaeus I lectin (four of four); they lacked epithelial markers other than cytokeratin (two of four). Four tumors were designated as angiomatoid carcinomas, based on staining for multiple epithelial markers: cytokeratin (four of four), epithelial membrane antigen (three of four), thyroglobulin (three of four). Three angiomatoid carcinomas also expressed or labeled with one or more vascular markers: CD34 (one of four), CD31 (two of four), Ulex europaeus I lectin (one of four), factor VIII-related antigen (one of four). The metastatic angiosarcoma to the thyroid gland labeled for factor VIII-related antigen, vimentin, CD31, and with Ulex europaeus I lectin. It did not express CD34. The six sarcomatoid carcinomas without angiomatoid features stained for cytokeratin (four of six), epithelial membrane antigen (one of six), and vimentin (six of six). None labeled for thyroglobulin, factor VIII-related antigen, CD31, CD34, or with Ulex europaeus I lectin. Angiomatoid carcinomas of the thyroid gland exhibit both epithelial and endothelial features. "Angiosarcoma" may represent the extreme in this spectrum of endothelial differentiation. All tumors behaved in a similar clinical fashion characterized by persistent local disease, widespread metastases and poor prognosis.