Mediastinal lymphoma.

Malignant lymphoma may involve the mediastinum as a component of disseminated disease or as a primary lesion. The most common types of primary mediastinal lymphomas (ML) are Hodgkin's disease (HD, usually of the nodular sclerosis type), large cell lymphoma (often associated with sclerosis), and lymphoblastic lymphoma (frequently seen in conjunction with acute lymphoblastic leukemia). The characteristic clinical, morphologic, and immunophenotypic features of these three neoplasms are reviewed. ML must be distinguished from Castleman's disease, an enigmatic lymphoid proliferation that frequently involves the mediastinum.