The eosinophilic variant of acute myelomonocytic leukemia developing as a secondary leukemia in a patient with mycosis fungoides

The eosinophilic variant of acute myelomonocytic leukemia (AMML) is highly associated with characteristic abnormalities of chromosome 16. Leukemias developing secondary to chemotherapy frequently show abnormalities of chromosomes 5 and 7. This report describes a secondary AMML, eosinophilic variant (M4Eo), developing in a patient with coexistent mycosis fungoides who had received chemotherapy, including an alkylating agent, and showing characteristic abnormalities of both chromosomes 7 and 16. This is the first reported case of the M4Eo arising secondarily in a patient treated for another hematopoietic malignancy, and the second case of treatment-induced M4Eo to show coexistent abnormalities of chromosomes 7 and 16. Additional cytochemical, ultrastructural, and cell surface marker findings are described supporting malignant transformation of the eosinophilic cell line.