Key Points

• Confirm specimen handling with the pathologist prior to the procedure in any patient with suspected intrathoracic lymphoma. Tissue may need to be transported in saline to allow for flow cytometric analysis.
• Chest tubes are usually unnecessary for management of pleural effusions in patients with newly diagnosed lymphoma. Effusions often resolve rapidly following the initiation of chemotherapy.
• Nodular sclerosis Hodgkin lymphoma and primary mediastinal large B-cell lymphoma are the most common mediastinal lymphomas and are often difficult to distinguish. Both are associated with extensive fibrosis, and large biopsies are often required to identify diagnostic malignant cells.
• Lymphoblastic lymphoma of the mediastinum, seen most commonly in children and young adult men, is a medical emergency requiring urgent initiation of therapy.
• Most patients with Hodgkin lymphoma or large cell lymphoma of the mediastinum have substantial residual masses after successful therapy, and repeat biopsy is not indicated in most cases.

Lymphomas are malignant neoplasms of lymphocytes and their precursor cells, the principal cellular elements of the immune system. Historically, lymphomas were classified merely by their histologic appearance, specifically cell size and architecture. The current classification system is the 2016 World Health Organization (WHO) system, which defines specific subcategories of lymphoma according to the immunologic, molecular, genetic, and clinical characteristics of the lymphoma cells as well as the morphology.[1][2]

Although most subtypes of lymphoma can potentially involve the mediastinum or lungs, only a few present as an isolated mediastinal or pulmonary mass. Those with the potential for a primary thoracic presentation are the focus of this chapter, specifically Hodgkin lymphoma (HL), primary mediastinal large B-cell lymphoma (PMBL), lymphoblastic lymphoma, and pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma. We discuss the pathology, clinical and laboratory features, staging, treatment, complications, and prognosis for each of these subtypes when they present in the mediastinum or lung.