SARCOMA OF THE PULMONARY-ARTERY - REPORT OF 4 CASES WITH ELECTRON-MICROSCOPIC AND IMMUNOHISTOCHEMICAL EXAMINATIONS, AND REVIEW OF THE LITERATURE

Herein we report the clinicopathological features of four cases of pul monary artery sarcoma that appeared at our institution during a period of 30 years. The patients, 2 males and 2 females, were 50-62 years ol d. Tumour was found in the pulmonary trunk and right pulmonary artery in all cases, in the pulmonary valve and left pulmonary artery in thre e of the four cases, and in the right ventricular outflow tract in one case. There was direct extension or metastases to the lungs in two ca ses, the heart in one case, mediastinum or lymph nodes in two cases an d the pleura in one case. Ultrastructural examination in one case reve aled cells with features of smooth muscle cells and myofibroblasts. Im munohistochemical examination of three cases gave the following result s: vimentin and smooth muscle specific actin was positive in all three cases, desmin in one case and cytokeratin in one case. No positivity was found for Factor VIII. This and other studies indicate that histol ogically most pulmonary artery sarcomas are leiomyosarcomas or ''undif ferentiated spindle cell sarcomas''. Immunohistochemical and ultrastru ctural examinations favour an origin from myofibroblasts, probably der ived from multipotent (undifferentiated) cells in the wall of the vess el. Most lesions show extensive intrathoracic growth although they rar ely metastasize outside the thoracic cavity. They have a poor prognosi s although some cases are currently being diagnosed during life.