Morphologic variants of acute promyelocytic leukemia in correlation with immunophenotypic profile

Abstract: BACKGROUND: Acute promyelocytic leukemia (APL) is a distinct and clinically urgent subtype of acute myeloid leukemia, characterized by specific morphological, immunophenotypic, and genetic features. Early recognition of APL is essential due to its association with severe coagulopathy and the need for prompt initiation of targeted therapy. Diagnostic challenges may arise, particularly in variant forms of APL, which can exhibit atypical morphology and overlapping immunophenotypic features with other acute leukemias. OBJECTIVES: The objective of this study is to assess the correlation between morphological variants of APL with their clinical, laboratory, and immunophenotypic characteristics. MATERIALS AND METHODS: This retrospective descriptive study was conducted at three major hematology centers in Basra, Iraq, over 6 years. A total of 57 patients with confirmed APL and complete clinical, morphological, and immunophenotypic data were included. Statistical analysis was conducted using the standard statistical software, with a significance level set at P < 0.05. RESULTS: The mean age of the study population was 26 ± 16.21 years, with a slight female predominance. Classical APL represented approximately two-thirds of cases, whereas the variant subtype accounted for one-third. Variant APL was significantly associated with fever and leukocytosis, while classical APL showed a higher frequency of Auer rods and pancytopenia. Immunophenotypic analysis demonstrated consistent findings between subtypes, although myeloperoxidase (MPO) expression was significantly higher in classical APL. CONCLUSION: Classical APL was the predominant subtype in this cohort, the variant APL associated with leukocytosis and fever, and classical APL more frequently presenting with Auer rods and pancytopenia. Immunophenotypically, MPO expression was significantly higher in classical APL.