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 phenotype. We query whether these two diseases are in fact different disorders or merely different stages of the same disease. Twelve ALL patients with a mediastinal mass and eleven NHL patients with a mediastinal mass under 15 years of age were studied with respect to cytogenetics, immunophenotype, genotype and clinical features. Clonal chromosome abnormalities 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 NHL). 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 abnormalities frequently detected in T cell ALL/NHL. In T-cell patients, immunophenotypical staging of ALL showed a predominance of early and common thymocyte phenotypes while that of NHL showed a predominance of common thymocyte phenotypes. All 7 of the T-cell patients examined showed rearrangements of the T-cell receptor beta chain gene. On the other hand, two non-T-cell, non-B-cell patients showed no rearrangement. There 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 the 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 receptor gene loci, i.e., 14q11-13 and 7q35, were most common and were observed at a high frequency in both groups, indicating that approximately 40%-70% of all lymphoblastic disorders with a mediastinal mass represent different stages of the same disorder. However, some translocations were associated only with NHL, indicating that some subsets of NHL with mediastinal mass may be different from ALL with a mediastinal mass. The cytogenetic profile and genotype of non-T-cell, non-B-cell patients were different from those of T-cell patients.