XXXX : report of four cases with electron microscopic and immunohistochemical examinations, and review of the literature.

@entity1 @entity2283 @entity242 @entity5 @entity1822 @entity358 @entity2277
Herein we report the clinicopathological features of four cases of @entity358 that appeared at our institution during a period of 30 years. The @entity1 , 2 males and 2 females, were 50-62 years old. @entity5 was found in the pulmonary trunk and right pulmonary artery in all cases, in the @entity358 in three 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 cases, the heart in one case, mediastinum or lymph nodes in two cases and the pleura in one case. Ultrastructural examination in one case revealed cells with features of smooth muscle cells and myofibroblasts. Immunohistochemical examination of three cases gave the following results: @entity2277 and smooth muscle specific actin was positive in all three cases, @entity2283 in one case and cytokeratin in one case. No positivity was found for Factor VIII. This and other studies indicate that histologically most pulmonary @entity242 are @entity1822 or "undifferentiated @entity242 ". Immunohistochemical and ultrastructural examinations favour an origin from myofibroblasts, probably derived from multipotent (undifferentiated) cells in the wall of the vessel. Most lesions show extensive intrathoracic growth although they rarely metastasize outside the thoracic cavity. They have a poor prognosis although some cases are currently being diagnosed during life.
