Hypergranular promyelocytic leukemia (APL): cytogenetic and ultrastructural specificity

Cytogenetic and ultrastructural findings were important diagnostic indicators of hypergranular promyelocytic leukemia (APL) in a patient whose bone marrow morphology appeared, by light microscopy, to be similar to that in acute myeloblastic leukemia (AML) with maturation. Peripheral blood smears and bone marrow specimens examined by light microscopy showed few cells with the numerous coarse, azurophilic granules typical of APL. Cytogenetic analyses, with several banding techniques, of cells from bone marrow and unstimulated peripheral blood revealed the 15;17 translocation, which has been observed only in APL. A reinterpretation of the reciprocal translocation, based on R banding, suggests that the breakpoints are distal to q24 in No. 15 and at or near the junction of q21 and q22 in No. 17. In addition, the patient had disseminated intravascular coagulation. The characteristic morphology of granules seen in APL was observed in this case only when transmission electron microscopy was used, since the granules were quite small. Since treatment for AML differs from that for APL, identification of the 15;17 translocation and ultrastructural evidence of granules represent valuable diagnostic aids for APL.