Diagnostic Immunophenotype of Acute Promyelocytic Leukemia Before and Early During Therapy With All-trans Retinoic Acid

Objectives: To study the immunophenotypic changes of acute promyelocytic leukemia (APL) in patients who recently received all-trans retinoic acid (ATRA) and to assess the diagnostic utility Blow cytome fry in this setting. Methods: Flow cytometry was performed on 29 newly diagnosed APLs and 93 other acute myeloid leukemias, including 25 HLA-DR or CD34 cases. Clinical notes from referring institutions were reviewed to assess for recent ATRA administration. Results: Recent ATRA therapy was documented in 17(59%) of 29 patients with APL. The main features of untreated APL were preserved with ATRA therapy, including CD34 (83% vs 82%), HLA-DR (83% vs 100%), and CD117+ (100% vs 77%). CD11b and CD11c were negative in all untreated APLs but positive in 76% and 88% of ATRA-treated APLs, respectively Optimal diagnostic criteria for untreated APL (CD34 or HLA-DR and CD11b and CD11c) showed 100% sensitivity and 98% specificity but were not useful after ATRA administration. The best interpretative approach to ATRA-treated APL (CD34 or HLA-DR) showed 100% sensitivity but limited specificity (73%). Conclusions: Information about recent ATRA administration is critical for adequate interpretation of the flow cytometric findings in patients with suspected APL.