The significance of ultrastructural features in acute myeloid leukemia: a study of 220 patients entered into the Medical Research Council's ninth acute myeloid leukemia trial.

Samples of peripheral blood or bone marrow obtained before treatment from 220 patients entered into the Medical Research Council's ninth acute myeloid leukemia (AML) trial were examined by electron microscopy. Several ultrastructural features showed strong correlations with each other, with variants of AML defined by the Hayhoe classification scheme, and with FAB type. However, no ultrastructural feature was found either uniquely in association with any other or specifically in any variant of AML. Each ultrastructural feature was tested for association with achievement of remission, remission duration, and survival time. Only Auer rods were associated with a high remission rate (p = 0.01), but even this association was not quite conventionally significant when the analysis was not quite conventionally significant when the analysis was stratified for age (p = 0.055). Shorter duration of remission was associated with cytoplasmic projections (p = 0.04 stratified for age). Overall survival was worse when convoluted or lobed nuclei were present but only when stratified for age and Hayhoe type (p = 0.04). The possibility of testing combinations of ultrastructural features for correlation with diagnosis or prognosis is discussed but would require data from more than the present 220 patients to be meaningful.