Trilineage phenotypic compromise in acute leukemia.

The expression of three lineage specific antigens in the leukemic blasts is extremely infrequent. We here report a case of triphenotypic acute leukemia with involvement of the myeloid and B and T lineages. The morphology of the blasts showed promyelocytic features with agranular cytoplasm, suggesting a M3-variant of AML. The blasts were positive for myeloperoxidase PAS and Sudan Black. Immunophenotype and cytogenetics did not confirm M3-AML diagnosis, showing a trilineage compromise (myeloid and T and B lymphoid markers) and the cytogenetic alterations +8 and +11, respectively. This report highlights the importance of correlating the results of multiple diagnostic methods in order to establish a correct diagnosis of mixed lineage acute leukemias, and allows evaluation of the prognostic importance of this subgroup of patients.