Childhood T-cell acute lymphoblastic leukemia with four distinct immunophenotypes representing different stages of T-cell development

The authors report on a 14-year-old boy who developed T-cell acute lymphobl astic leukemia (FAB:L1) displaying 4 immunophenotypically distinct leukemic cell populations by 3-color immunofluorescence staining Cytogenetic analys is at diagnosis showed 46,XY,add(4)(p16)[12]/46, XY[2]. A single rearrangem ent of the T-cell antigen receptor beta- and gamma -chain genes in these ce lls indicated monoclonality of the leukemic cells. These findings suggest t hat leukemic blast cells of monoclonal origin in this case were divided int o 4 immunophenotypic populations, representing various stages of differenti ation.