Diagnosis of acute promyelocytic leukemia – M3 according to the FAB classification
Acute promyelocytic leukemia and its atypical variant (M3 and M3v according to the FAB classification):
• accounts for 5–8% of all acute non-lymphoblastic leukemias (ONLL);
• part of the blasts has nuclei of characteristic lobed two-lobed shape;
• blasts, as a rule, contain abundant bright-colored grit and tufts of Auer rods, with an atypical microgranular variant (M3v), small grit is detected only by ultrastructural examination;
• blasts contain peroxidase, lipids, granulocyte esterase in the maximum amount, moderate amount of non-specific esterase resistant to sodium fluoride, PAS-positive substance in diffuse form;
• Immunophenotype is represented by expression of the myeloid antigen CD33, less often CD13 and CD15. Coexpression of CD2 and CD9 is sometimes observed. HLA-DR and CD34 are generally absent;
• in 95% of cases translocation is detected (15; 17) (q22; ql2); (PML / RARa). In addition to this translocation, t (ll; 17) (q23; q21), t (5; 17) (q32; 12), t (ll; 17) (ql3; q21) can also be observed. Acute promyelocytic leukemia in accordance with the WHO classification is distinguished into an independent category of acute non-lymphoblastic leukemia (ONLL) with repeated cytogenetic abnormalities.