An increase in basophils in a case of acute myelomonocytic leukaemia associated with marrow eosinophilia and inversion of chromosome 16.

A patient with acute myelomonocytic leukaemia (M4 subtype) with pericentric inversion of chromosome 16, inv(16)(p13q22), and a marked basophilia is described. Results from transmission electron microscopy suggested that the basophils were immature. Clinically, although leukaemic cells had a tendency to infiltrate a number of tissues and organs, such as skin, gingiva, liver and lung, the patient was successfully treated with chemotherapy. The increase in basophils accompanied by marrow eosinophilia may be the result of abnormal differentiation of leukaemic cells that have the capacity to differentiate into both the eosinophilic and basophilic pathways.