Dysplastic basophils can occur in the myelodysplastic syndromes but they are not diagnostically very useful as they are usually infrequent and the tendency of normal basophils to degranulate can make them difficult to recognize. They are much more readily recognized in the accelerated phase of chronic myelogenous leukemia (CML). The images shown are from the blood film of a 64-year-old woman with a 33-year history of Ph-positive CML. At the time of the film, she was about to commence bosutinib following relapse after a third autologous stem cell transplant. Splenectomy had been performed the year after presentation and during the course of her long illness she had also received busulfan, hydroxycarbamide, imatinib, and nilotinib. Her white cell count was 80.3 × 109/l and 87% of cells were basophils. She had become anemic and thrombocytopenic (hemoglobin 107 g/l and platelet count 17 × 109/l, respectively). The left hand image shows a dysplastic basophil (left) in comparison with a cytologically normal neutrophil (right). The cell in the center is a basophil precursor in which typical large basophilic granules can be recognized. The right hand image shows two dysplastic basophils. The dysplastic features, which were shown in the majority of basophils in this patient, included cytoplasmic vacuolation, nuclear hypersegmentation and granules that were sparse, abnormally small and had abnormal staining characteristics (often pink rather than purple on a Romanowsky stain).

At presentation of CML, the basophils are usually cytologically normal. The appearance of increased numbers of basophils and dysplastic basophils are common features of accelerated phase disease.