title: Acute myeloid leukemias M2 potentially misdiagnosed as M3 variant French-American-Britain (FAB) subtype: a transitional form?
abstract: From 1990 to 1994, 3 patients with de novo acute myeloid leukemia (AML) in whom light microscopy and cytochemistry suggested a FAB subtype M3 variant were observed at our Institute. Immunophenotype showed HLA-DR-, CD13+, CD33+, CD2+, CD9+; promyelocytic features were also detected by electron microscopy. However, leukemic cells lacked both translocation t(15;17) and RAR alpha/PML genes rearrangement. These cases were considered to be 'M2 atypical' subtypes and they contribute to point out how cytogenetics and molecular biology are mandatory for a correct diagnosis of acute promyelocytic leukemia (APL) particularly because therapy with all trans retinoic acid (ATRA) is now the best treatment for APL. Nevertheless these 3 cases indicate that the atypical M2 subtype may be confused with the M3v if only cytochemistry, immunophenotype and electron microscopy are used in the defining the FAB subtypes.
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007621:Karyotyping; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis*; D015473:Leukemia, Promyelocytic, Acute / Q000175:diagnosis*; D008297:Male; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D018168:Receptors, Retinoic Acid / Q000235:genetics; D000072482:Retinoic Acid Receptor alpha; D014157:Transcription Factors / Q000235:genetics; D014178:Translocation, Genetic; D025521:Tumor Suppressor Proteins
chemical_list: D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human