Acute promyelocytic leukemia with the pseudo-Chediak-Higashi anomaly and molecular documentation of t(15;17) chromosomal translocation.

Two morphologic variants of acute promyelocytic leukemia (AML M3) are recognized--the hypergranular form, in which Auer rods are usually numerous; and the microgranular form. The case of AML M3 reported here lacked numerous Auer rods but was hypergranular and demonstrated prominent giant Chediak-Higashi-like granules in the leukemic cells. Although routine karyotypic studies were inconclusive, at t(15;17) translocation was documented using Southern blot genotypic analysis and probes for the retinoic acid receptor-alpha and pml genes. This is the first case of this unusual morphologic anomaly in which the granules are described in routine histologic sections and the first with evidence of a t(15;17) chromosomal translocation. It also illustrates the importance of Southern blot analysis in suspected cases of AML M3 with "negative" karyotypic studies.