Color Atlas of Hematology - Practical Microscopic and Clinical ...

104Abnormalities of the White Cell SeriesAcute Lymphoblastic Leukemia (ALL)ALL are the leukemias in which the cells do not morphologically resemblemyeloblasts, promyelocytes, or monocytes, nor do they show the correspondingcytochemical pattern. Common attributes are a usually slightlysmaller cell nucleus and denser chromatin structure, the grainy consistencyof which can be made out only with optimal smear technique (i.e.,very light). The classification as ALL is based on the (often remote) similaritiesof the cells to lymphocytes or lymphoblasts from lymph nodes, andon their immunological cell marker behavior. Insufficiently close morphologicalanalysis can also result in possible confusion with chronic lymphocyticleukemia (CLL), but cell surface marker analysis (see below) will correctthis mistake. Advanced diagnostics start with peroxidase and esterasetests on fresh smears, performed in a hematology laboratory, togetherwith (as a minimum) immunological marker studies carried out on freshheparinized blood samples in a specialist laboratory. The detailed differentiationprovided by this cell surface marker analysis has prognostic implicationsand some therapeutic relevance especially for the distinction tobilineage leukemia and AML (Table 16).Table 16 Immunological classification of acute bilineage leukemias (adapted from Bene MCet al. (1995) European Group for the Immunological Characterization of Leukemias (EGIL) 9:1783–1786)Score B-lymphoid T-lymphoid Myeloid2 CytCD79a* CD3(m/cyt) MP0Cyt IgManti-TCR1 CD19 CD2 CD117CD20 CD5 CD13CD10 CD8 CD33CD10CD650.5 TdT TdT CD14CD24 CD7 CD15CD1aCD64* CD79a may also be expressed in some cases of precursor T-lymphoblastic leukemia/lymphoma.