Ultrastructure of acute myeloid leukemia arising in multiple myeloma.

Bone marrow from a case of multiple myeloma in which acute myeloid leukemia supervened four years after diagnosis was examined with the electron microscope. Two distinct populations of neoplastic cells, one plasmacytoid and the other myeloid, were identified in the marrow. It is concluded that the acute leukemia that developed in this patient was a distinctly new neoplasm arising from the myeloid series of cells. Since in nearly all previously reported cases, and in our patient, alkylating agents had been administered, it is thought that this may have been a factor in the development of acute myeloid leukemia.