Immunohistochemical demonstration of the endothelial nature of aortic intimal sarcoma.

Primary sarcomas of the aorta are rare; fewer than 30 cases have been reported. Among these, the majority are intraluminal and apparently intimal in origin. Extensive histochemical and electron-microscopic evaluation of these tumors has not previously been performed. We present a case of aortic intimal sarcoma in a 70-year-old man whose resected aorta showed multifocal, intimal tumor that appeared on light microscopy to be undifferentiated sarcoma. Electron microscopy was not helpful; however, immunohistochemical studies confirmed the endothelial nature of this neoplasm. The multifocal pattern of the tumor and the presence of intervening, atypical, proliferative endothelial cells suggests that endothelial dysplasia may have been a precursor lesion.