Primary large cell lymphomas of the mediastinum: an analysis of 20 cases.

Malignant lymphomas originating primarily in the mediastinum consist predominantly of Hodgkin's disease of the nodular sclerosis type, lymphoblastic lymphomas, and large cell non-Hodgkin's lymphomas of diffuse growth pattern (DHL). This analysis of 20 cases of primary mediastinal DHL presents the clinical and pathologic findings in nine patients with T-immunoblastic sarcoma (T-IBS), six with sclerosing variants of follicular center cell lymphoma (FCCL), and five with B-immunoblastic sarcoma (B-IBS). T-IBS patients were predominantly young adult women (mean age 31 years) presenting with relatively well confined mediastinal tumors; four of nine manifested the SVC syndrome. The immunomorphologic findings in T-IBS were similar to those of node-based peripheral T-cell lymphomas. Patients with FCCL and B-IBS were predominantly men, exhibited a broad age range, and presented with larger tumors with a high incidence of contiguous involvement of intrathoracic structures (83% in FCCL, 60% in B-IBS). Chemotherapeutic intervention attained CR in 19 of 20 patients, with 14 of 20 remaining alive in relapse-free CR a median of 26 months after completion of therapy. Durable CR was attained in eight of nine T-IBS patients, in four of six patients with FCCL, and in three of five patients with B-IBS. The morphologic features of these lymphoma subtypes are presented in detail and discussed in relation to the complex differential diagnosis of mediastinal neoplasms.