Acute basophilic leukemia: case report

The term "basophilic leukemia" has been in use for 75 years. However, consistent diagnostic criteria are lacking. This is due to the rarity of the disease and to the routine unavailability of special tests that are often required to confirm a diagnosis. We report an unusual case of acute basophilic leukemia in a child who was referred to our Center, arriving with partially treated acute lymphoblastic leukemia. Basophilic differentiation on light microscopy was evident from the coarse basophilic granules in blasts, a progressive maturation of blasts toward basophils, and toluidine positivity on cytochemistry. Blasts showed a myeloid immunophenotype (CD13+, CD33+, CD117+) with a characteristic dual positivity for CD34 and CD25, highly suggestive of basophilic nature of the blasts. Conventional cytogenetic studies revealed translocation t(8;21)(q22;q22). A diagnosis of acute basophilic leukemia with t(8;21) was made. Review of pre-therapy slides showed features consistent with AML-M2 with basophilia. There were no basophilic blasts. With these features, a diagnosis of acute basophilic leukemia secondary to AML-M2 was made. In our patient, basophilic leukemia appears to have evolved from selective clonal proliferation of "basophil-committed blasts" during the course of the disease in a case of AML-M2 with basophilia.