Platelet granulopathy: a new morphologic feature in preleukemia and myelomonocytic leukemia: light microscopy and ultrastructural morphology and cytochemistry.

We have previously reported on the ultrastructure of platelets in preleukemia and myelomonocytic leukemia. We referred to an unusual and distinct anomaly of the platelet granules found in 15 of 16 patients. In the present communication we wish to describe and illustrate the light microscopic appearance of giant anomalous granules. Close scrutiny of the platelet morphology and a search for the aforementioned platelet granulopathy are important in the evaluation of patients with myeloproliferative diseases. In this paper we describe and illustrate in more detail the ultrastructure and ultrastructural histochemistry of the abnormal granules. In those patients with the platelet granulopathy, we have conducted in vitro platelet aggregation studies and carried out an electron microscopic evaluation of the aggregates. At least some of the giant granules remained morphologically intact in advanced stages of the aggregation phenomenon, and thus they are probably composed of elements that were not released during aggregation.