Angiosarcoma of the thyroid: a light, electron microscopic and histoimmunological study.

A histologic, histoimmunological, and ultrastructural study of a primary angiosarcoma of the thyroid gland is reported. The occurrence of neoplastic cells positive for Factor VIII-related antigen and Ulex Europaeus Agglutinin-I and the presence in their cytoplasms of Weibel-Palade bodies are consistent with this diagnosis. These findings further support the view that primary angiosarcoma of the thyroid is a distinct pathological entity and should no longer be interpreted as a variant of a poorly differentiated carcinoma.