Rapid Diagnosis of Acute Promyelocytic Leukemia by Analyzing the Immunocytochemical Pattern of the PML Protein With the Monoclonal Antibody PG-M3

Abstract

The fusion protein, promyelocytic leukemia–retinoic acid receptor (PML-RAR)alpha, generated by the t(15;17) translocation has an abnormal cellular distribution with colocalization of RARalpha and PML proteins. We analyzed the immunostaining pattern of PML protein using the PGM3 monoclonal antibody directed against the amino terminal portion of PML (retained in wild-type PML and PML-RARalpha fusion protein) in the diagnosis of acute promyelocytic leukemia (APL). In addition, we compared this test with other methods for detecting the PML-RARalpha fusion gene. A normal immunostaining pattern was observed in nonmyeloid disorders and in 78 of 111 acute myeloid leukemias (AMLs). A microgranular pattern was observed in 25 AMLs, all corresponding to APL. These results were concordant with the reverse transcriptase–polymerase chain reaction results for PML-RARalpha fusion gene. Only 1 case positive for the PML-RARalpha transcript showed a normal protein pattern by immunocytochemistry. PML immunostaining was helpful to rapidly differentiate 7 cases with borderline characteristics and to obtain the diagnosis in 2 cases with scarce material. The effectiveness and low cost of this technique support its routine use as a first-line procedure in the differential diagnosis of AML.