Malignant endothelioma of the aorta.

An untreated case of a malignant endothelial tumour of the thoracic aorta of a 67 year-old male is reported. A tumour, 7 x 6 x 1.5 cm in size occupied the lumen of the descending thoracic aorta and two daughter lesions, 0.5 cm in diameter, were located in the abdominal aorta and the left common iliac artery. Histologically, they were composed of a surface cellular lining and a underlying necrotic mass; the former was six to ten layers of bizarre epithelioid cells thick and the latter contained much nuclear debris. Innumerable tumour emboli of epithelioid tumour cells and producing ischaemic lesions were found in various organs and tissues. Ultrastructurally, tumour cells were arranged in acinar pattern with narrow lumena and immature basement membrane. There were ultrastructural appearances interpreted as Weibel-Palade bodies and immunohistochemically factor VIII related antigen and vimentin was seen in the tumour cells.