Non-mesothelial Tumors of the Pleura

Primary tumors of the pleura are relatively rare both in children and adults. Metastatic disease to the pleura is the most common neoplastic process involving the pleural surfaces and far outnumbers primary benign and malignant pleural neoplasms. Malignant mesothelioma represents the most common primary malignant neoplasm of this site, with an estimated 2000 newly diagnosed cases in the United States each year [Cagle and Allen, Respirology 16:430-438, 2011; English and Leslie, Clin Chest Med 27:157-180, 2006; Ai and Stevenson, Oncologist 19:975-984, 2014]. Aside from malignant mesothelioma, there is a variety of more uncommon primary pleural neoplasms, both benign and malignant, that need to be considered in the differential diagnosis. Since many of these entities can demonstrate similar clinical, imaging, and macroscopic features, awareness of these conditions as well as accurate histopathologic diagnosis is extremely important as the treatment and prognosis for these diverse tumors can vary greatly. Novel immunohistochemical and molecular markers allow for a confirmatory diagnosis in some of the entities; however, careful morphologic assessment and evaluation of the clinical context are indispensable for the correct diagnosis, not only to distinguish between different primary pleural neoplasms but also to exclude metastatic disease. This chapter provides an overview of the most common primary pleural neoplasms other than malignant mesothelioma and reviews their typical clinical presentation as well as morphologic, immunophenotypic, and molecular characteristics.