Tumors of the Pulmonary Vascular Bed

Abstract

Primary or secondary tumors of the lung can affect all levels of the pulmonary vascular bed, including the pulmonary arteries, veins, and capillaries. Most primary tumors of the pulmonary vasculature are poorly differentiated, highly fatal sarcomas of the large main pulmonary arteries and veins. Pulmonary arterial sarcoma (PAS) is far more prevalent than its venous counterpart, although both arterial and venous sarcomas are quite rare. Secondary involvement of the pulmonary vasculature by other primary lung cancers or metastatic malignant neoplasm is not as rare, however. Direct extension of pelvic sarcomas to pulmonary arteries via the central venous system and the right side of the heart has been documented as well. Pulmonary capillary hemangiomatosis (PCH) is an elusive entity and has been considered either as a low-grade neoplasm or a as tumorlike lesion of pulmonary capillaries. PCH typically causes severe pulmonary hypertension that is often accompanied by fatal right-sided heart failure. Most aortic sarcomas and PASs are intimal sarcomas and that most sarcomas of the pulmonary veins and inferior vena cava are mural leiomyosarcomas. Mural sarcomas of the inferior vena cava constitute the largest subgroup of the primary tumors arising in the great blood vessels. The incidence of pulmonary vein sarcomas (PVSs) is far lower than that of PASs. Most intimal sarcomas of the aorta and the pulmonary arteries in that study were poorly differentiated or undifferentiated sarcomas with a prominent intraluminal growth pattern, immunohistochemical evidence of myofibroblastic differentiation, and a poorer prognosis than the mural leiomyosarcomas in the inferior vena cava and the pulmonary veins. This chapter focuses on the current clinicopathological concepts of the primary sarcomas of pulmonary arteries and veins. In light of the unclear biologic nature of PCH, nonneoplastic as well as neoplastic aspects of PCH are discussed although the main focus of this chapter is on the neoplastic diseases of the pulmonary vasculature. Manifestations of secondary tumors mimicking a primary pulmonary vascular tumor or idiopathic pulmonary hypertension are also covered briefly.