Phenotypic heterogeneity at the DNA level in childhood leukemia with a mediastinal mass

Acute lymphoblastic leukemia and non-Hodgkin's 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 of 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Poor prognosis of mediastinal non-Hodgkin's lymphoma with an immature phenotype of CD2+, CD7 (or CD5)+, CD3-, CD4-, and CD8-

Nine children with mediastinal non-Hodgkin's lymphoma (NHL) were treated according to our new regimen which is characterized by intensified therapy with high-dose cytosine arabinoside (HDCA). After induction therapy with a combination of five drugs, such as vincristine, doxorubicin, cyclophosphamide, 1-asparaginase, and prednisolone, intermediate dosages of methotrexate (MTX) (1 g/m2) and HDCA (1.5 g/m2 x 12 doses) were administered. All but one patient (88.9%) achieved complete remission and then received this intensified therapy. With a median follow-up period of 25.5 months, five patients are still in complete remission, but three patients have relapsed. From the phenotypic point of view, these relapsed patients showed only very immature T-cell differentiation antigens such as CD2 and CD7 (or CD5). These results suggest that HDCA as intensified therapy for children with mediastinal NHL seems to be effective. However, for patients with an immature phenotype of T-lineage cells, more sophisticated regimens should be prepared.

Concomitant rearrangements of T-cell beta- and gamma-chain genes in childhood T-lineage leukemia/lymphoma

Similar to the immunoglobulin (Ig) gene rearrangements in B-lineage cells, identification of T-cell receptor (TCR) gene rearrangements is a novel clonal marker and necessary to establish a T-cell lineage. The function of T-cell gamma-chain (T gamma) gene is still unknown, but because of its shared properties with T-cell alpha-chain (T alpha) and T beta genes, we analysed T gamma gene organization in 10 patients with T-lineage leukemia/lymphoma as well as in non-T lineage leukemias. All 10 cases of T-lineage leukemia/lymphoma, whose phenotypes were different, demonstrated T gamma gene rearrangements as well as T beta gene rearrangements. In contrast, among the non-T-lineage leukemias, the emergence of T beta and/or T gamma gene rearrangements was varied. Based on these findings, concomitant rearrangements of T beta and T gamma genes are characteristic in childhood T-lineage leukemia/lymphoma regardless of their phenotypic differences. Furthermore, no obvious developmental hierarchy was observed between T beta and T gamma gene arrangements in these leukemia/lymphoma cells.