AIDS-related non-Hodgkin's lymphomas: from pathology and molecular pathogenesis to treatment.

In the highly active antiretroviral therapy (HAART) era, AIDS-related non-Hodgkin's lymphomas (AIDS-NHL) and their treatment still represent an open issue, because HAART may not be sufficient to prevent the development of NHL. The present spectrum of AIDS-NHL includes systemic lymphomas, primary central nervous system lymphomas, and 2 rare entities, primary effusion lymphomas (PEL) and plasmablastic lymphomas of the oral cavity. The vast majority of systemic AIDS-NHL belongs to 3 high-grade B-cell lymphomas: Burkitt's lymphoma (BL), immunoblastic lymphoma (IBL), and large-cell lymphoma (LCL). The pathologic heterogeneity of AIDS-NHL is correlated with the heterogeneity of the molecular lesions associated with these lymphomas. The molecular lesions associated with AIDS-BL involve activation of c-MYC inactivation of p53, and infection by Epstein-Barr virus (EBV). EBV infection occurs in 40% of LCL cases and in 90% of IBL cases. Rearrangements of BCL-6 are detected in 20% of AIDS-LCL cases. In the presence of EBV infection, BCL-6 expressing AIDS-LCL fails to express the latent membrane protein 1 (LMP1) antigen. Conversely, AIDS-IBL are characterized by absent BCL-6 expression, absence of BCL-6 rearrangements, and frequent expression of LMP1. Consistently, the molecular pathways of viral infection and lesions of cancer-related genes associated with AIDS-NHL vary substantially in different clinicopathologic categories of the disease. The marked degree of biologic heterogeneity of AIDS-NHL is highlighted by their histogenetic differences, because AIDS-NHL are related to distinct B cell subsets (ie, germinal center [GC] or post-GC B cells). The phenotypic pattern of AIDS-BL and systemic AIDS-LCL closely reflects B cells residing in the GC, namely centroblasts and centrocytes. Conversely, the phenotype of AIDS-IBL, either systemic or localized primarily to the central nervous system, and AIDS-PEL reflects post-GC B cells in all cases. New information on the molecular and virologic pathogenesis of AIDS-NHL may serve as a point of attack for pathogenic-driven therapies. Moreover, a greater knowledge of other biologic features of these tumors may help investigators identify new potential targets for "intelligent" therapies.