ACUTE LYMPHOBLASTIC-LEUKEMIA AND NON-HODGKINS-LYMPHOMA WITH MEDIASTINAL MASS - A STUDY OF 23 CHILDREN - DIFFERENT DISORDERS OR DIFFERENT STAGES

Mediastinal tumor was found in both acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). Most cases showed the T-cell phenot ype. We query whether these two diseases are in fact different disorde rs or merely different stages of the same disease. Twelve ALL patients with a mediastinal mass and eleven NHL patients with a mediastinal ma ss under 15 years of age were studied with respect to cytogenetics, im munophenotype, genotype and clinical features. Clonal chromosome abnor malities were found in 75% (9/12) of the ALL patients and 100% (11/11) of the NHL patients. Of the 20 patients with chromosome abnormalities , 12 (60%) had translocations involving 14q11-13 and 7q35 (8 ALL, 4 NH L). t(9;17)(q34;q23) was found only in 3 patients with NHL. All showed the T-cell phenotype except two, who had none df the chromosomal abno rmalities frequently detected in T cell ALL/NHL. In T-cell patients, i mmunophenotypical staging of ALL showed a predominance of early and co mmon thymocyte phenotypes while that of NHL showed a predominance of c ommon thymocyte phenotypes. All 7 of the T-cell patients examined show ed rearrangements of the T-cell receptor beta chain gene. On the other hand, two non-T-cell, non-B-cell patients showed no rearrangement. Th ere were no apparent clinical differences between ALL and NHL patients in age (median 8.6 vs 8.9 years), sex ratio (F/M 9/3 vs 7/4) or in th e rate of complete remission (90% vs 100%). Our study demonstrated no relevant clinical, prognostic, or immunophenotypic differences between ALL and NHL with mediastinal mass. Translocations involving T-cell re ceptor gene loci, i.e., 14q11-13 and 7q35, were most common and were o bserved at a high frequency in both groups, indicating that approximat ely 40%-70% of all lymphoblastic disorders with a mediastinal mass rep resent different stages of the same disorder. However, some translocat ions were associated only with NHL, indicating that some subsets of NH L with mediastinal mass may be different from ALL with a mediastinal m ass. The cytogenetic profile and genotype of non-T-cell, non-B-cell pa tients were different from those of T-cell patients.