Blastic transformation of a well-differentiated monocytic leukemia: changes in cytochemical and cell surface markers.

The clinical course of a patient with a well-differentiated monocytic leukemia which later underwent blastic transformation is described. Cytochemical, ultrastructural and cell surface analysis data were obtained at periods throughout her illness and correlated with the blastic transformation. Although surface markers characteristic of monocytic leukemia persisted, a deficiency of peroxidase in the granules of this patient's monocytes was observed as well as loss of alpha-naphthyl butyrate esterase staining during transformation.