Immunophenotype of Pediatric ALL

Flow cytometric immunophenotyping still stands on a significant position as a diagnostic tool against acute lymphoblastic leukemia (ALL). Improvement of flow cytometry (FCM) instrument and increasing availability of monoclonal antibodies and fluorochromes enable multicolor analysis and accurate diagnosis. But molecular diagnostic method also made a big progress especially in genome-wide analysis. The World Health Organization (WHO) classification of tumors of the hematopoietic and lymphoid tissues was first established in 2008, then in 2017 it was revised diagnostic criteria including morphologic, phenotypic, and more genotypic features (Wenzinger et al., Curr Hematol Malig Rep 13:275–288, 2018). Thus, such a recent progress of genomic analysis alters a role of immunophenotyping for pediatric ALL. Currently, entities of pediatric ALL are divided into subtypes by not only immunophenotyping but various cytogenetic abnormalities. Immunophenotyping may become no longer crucial but only exist to decide initial treatment until an identification of cytogenetic abnormalities in the near future. However, recently it turned out that immunophenotypic patterns indicate a specific feature according to each cytogenetic abnormality. To predict cytogenetic abnormality based on specific immunophenotype may fulfill an efficient cytogenetic diagnosis for most of known cytogenetic abnormalities. This chapter indicates the present situation of flow cytometric testing and current application for pediatric ALL, based on a new era of genomic analysis.