ABSTRACT
Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is defined pathologically by a diffuse proliferation of large cells thought to derive from thymic B cells and often compartmentalized by fine bands of sclerosis. It primarily occurs in young, adult females with primary involvement of the mediastinum and is often associated with locally invasive behavior. Molecular studies of PMBCL can show discrepant results, which may reflect the heterogeneity of the cases studied in the absence of strict diagnostic criteria for PMBCL. The International Prognostic Index was originally developed in diffuse large cell lymphoma prior to the recognition of PMBCL. A major challenge in the management of PMBCL is the evaluation of a residual mass following chemotherapy, and whether it represents active lymphoma. There is poor correlation between the size of a residual mass on computed tomography and the risk of relapse. Gallium scintigraphy has been used to detect persistent viable tumor in patients with a residual mass after therapy.
