Unusual cytochemical reactivity for toluidine blue in granular acute lymphoblastic leukemia: a report of two rare cases

Abstract

Azurophilic granulation of blasts is a feature of acute myeloid leukemia (AML). Granular acute lymphoblastic leukemia (ALL) may mimic AML due to the presence of cytoplasmic granules in lymphoblasts, but cytochemistry and immunophenotyping are helpful in making the correct diagnosis. Toluidine blue (TB) is a metachromatic dye, which stains basophils and myeloid blasts that exhibit basophilic differentiation. Reactivity for TB has not been described in lymphoblasts. We herein report two cases of granular ALL with blasts exhibiting reactivity for TB that caused diagnostic dilemma. Immunophenotyping and cytogenetic studies were helpful in making a correct diagnosis. This report of two rare case highlight the reactivity of lymphoblasts with TB not hitherto described and the importance of a detailed diagnostic work-up in acute leukemia.