Categories of T-ALL. T-ALLs were divided into 3 major immunophenotypic categories: (1) αβ lineage cases (n = 66), which include cases expressing TCRαβ (n = 24) and pre-αβ T-ALLs, which are TCR- but express cTCRβ+ (n = 42); (2) T-ALLs expressing TCRγδ (n = 32); and (3) immature (IM) T-ALLs, which are TCR- and cTCRβ - (n = 46). IM T-ALLs were classified on the basis of their TCRδ, TCRγ, and TCRβ gene configurations. IM0 cases demonstrate a germline configuration at all 3 loci and include the most immature, nonlineage-restricted cases. Progressive T-lymphoid restriction is associated with TCRδ rearrangement (IMδ), followed by TCRγ and incomplete TCRβ DJ in IMγ, and finally by complete TCRβ V(D)J rearrangement in IMβ, the immediate precursors of αβ lineage T-ALLs.16 The incidence of CALM-AF10 in 131 unselected T-ALLs in each subgroup is indicated. sTCR indicates surface TCR; cTCR, cytoplasmic TCR; GL, germline.
