And Tcell Lineage

More recently, classification of ALL has been based on B- and T-cell lineage.54 More than 80% of cases of ALL in adults are of B-cell lineage, with 10-15% arising from T cells.18'54,55 While protocol chemotherapy and overall treatment usually follow similar pathways, prognosis may be dictated by these subsets and their individual responses to treatment or propensity for relapse.10,33

As the B- and T-cell classifications have evolved, these classifications have now been subdivided into diagnostic groups based on immunophenotypic groups extended to specific genetic mutations, and genomics. Treatment planning follows subset or subgroup analysis, including T-cell and mature B-cell ALL, pre-B ALL, and ALL with associated bcr/abl translocation t(9;22), or other detrimental abnormalities demonstrated. These differences in intensity of treatment and various versions of protocols will be considered in Chapter 13.410 Prognosis can now be related to specific subsets based on chromosome mutation and cell signaling pathways; the best examples of these cases, once again, are t(9;22) and t(4;11) as unfavorable predictors, while others may predict a more favorable response and prognosis.10

MORPHOLOGY, IMMUNOPHENOTYPE, AND CYTOGENETICS

Classifications based on morphology, immunopheno-type, and cytogenetics (MIC) have further defined subsets of disease based on these parameters for ALL (MIC) and AML (MIC-M), and employ defined subsets of antibodies to delineate diagnostic groups.56-58 Differences in B- and T-cell incidence in children and adults respectively are detailed in an elegant manner by Pui (Table 10.1). These also relate B- and T-cell lineage to specific subsets of chromosome abnormalities and their incidence by comparison in children and adults.

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