New flow cytometry in hematologic malignancies

Abstract

Ymphoblastic leukemia/lymphoblastic lymphoma represents a heterogeneous group of neoplasms arising from lymphoblasts committed to either the B- or T-cell lineage. The term acute lymphoblastic leukemia (ALL) is reserved for those cases with extensive involvement of bone marrow or peripheral blood, with 25% bone marrow blasts as a commonly used threshold for defining ALL. The laboratory diagnosis of ALL is complex and is based on cytomorphological, immuno- logical, cytogenetic and molecular analysis. Detailed immunophenotyping of leukemic blasts distinguishes several differentiation stages of B- or T-lymphoblasts: early precursor B-ALL or pro-B-ALL, common B-ALL, and pre-B-ALL for B-lineage lymphoblasts; and pro-T- ALL, pre-T-ALL, cortical T-ALL and medullary T-ALL. 1,2 Over the years, the association between the presence of specific genomic abnormalities with distinct clinical or phenotypic features, or therapeutic responses and sur- vival has led to the recognition of several distinct clinico- biological entities. Among the B-ALL with recurrent genetic abnormalities, the new 2008 WHO classification now recognizes seven genetic entities: B-ALL with t(9;22)(q34;q11); B-ALL with t(v;11q23), B-ALL with t(12;21)(p13;q22), B-ALL with hyperdiploidy, B-ALL with hypodiploidy, B-ALL with t(5;14)(q31;q32) and B-ALL with t(1;19)((q23;p13). In addition to these specific enti- ties, many other recurrent genetic abnormalities have been reported in B-ALL as well as in T-ALL. The prognos- tic significance of specific genomic lesions has been incorporated into risk stratification and risk-adapted therapy.