Immunofluorescent analysis with the anti-PML monoclonal antibody PG-M3 for rapid and accurate genetic diagnosis of acute promyelocytic leukemia

Genetic diagnosis is currently considered the most reliable method to accurately identify patients with acute promyelocytic leukemia (APL) requiring tailored therapy including all-trans retinoic acid (ATRA). We investigated the clinical effectiveness of immunofluorescence techniques with the anti-PML monoclonal antibody PG-M3 for rapid and accurate diagnosis of APL. PML immunofluorescence staining was analyzed in 164 patients with acute myeloblastic leukemia (AML), including APL (110 patients) and non-APL subtypes (54 patients). All 54 patients with an AML phenotype, in whom tests for t(15;17) or its fusion gene PML/RAR were negative, showed a speckled (macrogranular) nuclear pattern. Of the 110 genetically diagnosed APL patients, 108 showed a microgranular pattern that confirmed PG-M3 positivity. The remaining two patients were not evaluable for PG-M3 reactivity because of scarcity of cells. No patient with APL showed a normal pattern. The high sensitivity and specificity of immunolabeling using PG-M3 monoclonal antibody show that it is a highly efficient and reliable tool to identify PML/RAR-positive patients with APL and that it should be standardized as a first-line diagnostic procedure. In addition, it is technically simple, fast, and cheap, only requiring small tissue samples and non-sophisticated equipment.