According to the FAB (French-American-British) classification, two main cytological subtypes are recognized: the classical hypergranular and the microgranular variant. However, other morphological variants have been reported in the literature. Therefore, careful examination is needed to diagnose acute promyelocytic leukemia (APL). Herein, the case of an APL variant, with basophil-like granules, occurring in a 65 year-old woman admitted due to high fever is reported. The peripheral blood showed blasts and increased basophils. A bone marrow smear showed leukemic blasts, with irregular nuclei and coarse basophil-like granules, in the cytoplasm. Cytoplasmic vacuoles were also noted, but no Auer rod was found. The blasts showed positivity toward MPO, tryptase and toluidine blue staining. The immunophenotypes revealed a myeloid lineage, with aberrant expression of CD2 and CD7. The karyotype was t(15;17)(q22;q12) in 17 out of 20 metaphases. The RT-PCR was positive for long form PML/RARՁ transcripts. Four weeks after chemotherapy, her bone marrow status findings were in complete remission, with the karyotype converted to normal. Basophil-like granules in the blasts and promyelocytes became decreased during the course of all-transretinoic acid (ATRA) treatment. The chimeric transcript of PML/RARՁ converted to negative after consolidation chemotherapy.

Keywords: Leukemia, Promyelocytic, Acute, Variant, Basophils