Adult lymphoblastic lymphoma.

Adult lymphoblastic lymphoma (LBL) is an aggressive form of non-Hodgkin lymphoma occurring in predominantly adolescent and young adult men. Lymphoblastic lymphoma is rare, accounting for 1% to 2% of all non-Hodgkin lymphomas and is of T-cell phenotype in 90% of cases. Lymphoblastic lymphoma is morphologically indistinct from acute lymphoblastic leukemia (ALL). Both express their lineage-specific markers as well as terminal deoxynucleotidyl transferase. The differences are often made on clinical grounds. Lymphoblastic lymphoma is characterized by a predominantly nodal distribution of disease, often with a large mediastinal mass. Patients with less than 25% bone marrow involvement have typically been categorized as LBL rather than ALL, although this has not been applied consistently in the literature. Gene expression studies have identified differences in gene expression, with LBL expressing higher levels of genes associated with cytoskeleton, adhesion, angiogenesis, and chemotaxis than ALL. Although LBL and ALL can be distinct clinically, chemotherapy strategies are often very similar. Acute lymphoblastic leukemia regimens, which incorporate intensive multidrug induction, consolidation, delayed intensification, and maintenance, have been shown to be superior to standard lymphoma regimens. As central nervous system (CNS) relapse is common, CNS prophylaxis with high-dose chemotherapy and intrathecal therapy is also standard. The prophylactic use of CNS irradiation has declined with the introduction of chemotherapy regimens incorporating high doses of CNS-penetrating drugs such as cytarabine and methotrexate. The use of consolidative radiation to the mediastinum remains uncertain. High-dose chemotherapy followed by autologous or allogeneic transplantation as consolidation for patients in CR1 is controversial with modern intensive chemotherapy regimens, although transplantation has a proven role in the relapse setting.