Primary mediastinal large cell lymphoma

PURPOSE: Primary mediastinal large cell lymphoma PMLCL is a recently described entity which has provoked considerable interest lately. The unique immunophenotype of the malignant cell, as well as conflicting reports regarding its response to therapy, prompted us to review the current literature focusing on the pathological and clinical aspects of this disease. DESIGN: We reviewed the current literature that contained details on the clinical presentation, pathological profile and clinical outcome. RESULTS: Most reports agree that PMLCL typically affects a young female population and presents with symptoms related to compression of mediastinal structures. Pathologically, the malignant cells may arise from a distinctive thymic medullary B cell subpopulation which is characterized by the following phenotype: CD19+, CD21-, CD20+, CD22+. Alterations of c-myc and lack of expression of HLA class 1 antigens on the tumour cell surface have been described. Response to treatment and clinical outcome have varied from one series to another and is possibly explained by the small number of patients in most series and by the heterogeneity of therapy. In general, the outcome does not appear to be worse than that of other large cell lymphomas although, given the young age of these patients, it might be expected to be more favourable. CONCLUSIONS: Primary mediastinal large cell lymphoma is a distinct clinico-pathological entity characterized by: (1) a predominance of young adults; (2) female predominance (female/male ratio of 2:1) in contrast to the other large cell lymphomas; (3) CD19+/CD21- immunophenotype; (4) absence of HLA-class 1 antigen expression; (5) possible involvement of c-myc; (6) frequent dissemination at relapse to unusual anatomic sites in a pattern reminiscent of Burkitt's lymphoma. The role of radiotherapy and the optimal treatment for this disorder are issues that remain unresolved.