Inter-observer variance and the need for standardization in the morphological classification of myelodysplastic syndrome

•Nearly 100,000 hematopoietic cell morphology from 499 MDS patients were evaluated.•Inter-observer variance in the assessment of dysplastic features of MDS was found.•Observers didn’t recognize hypo–granularity unless almost all granules are absent.•Pseudo Pelger–Huët anomaly was overlooked except for morphologically typical cells. In this era of genome medicine, the sub-classification of myeloid neoplasms, including myelodysplastic syndrome (MDS), is now supported by genetic testing in selected cases. However, as the initial suspicion and primary diagnosis of the disease still largely relies on morphological features and numbers of hematopoietic cells, the establishment of a uniform diagnostic basis, especially for cell morphology, is essential. In this study, we collected nearly 100,000 hematopoietic cell images from 499 peripheral blood smear specimens from patients with MDS and used these to evaluate the standardization of morphological classification by medical technologists. The observers in this study ranged between two to eleven for each image, and the images were classified according to MDS criteria through a web-based system. We found considerable inter-observer variance in the assessment of dysplastic features. Observers did not recognize cytoplasmic hypo–granularity unless almost all granules in neutrophils were absent. Pseudo Pelger–Huët anomalies were also often overlooked, except for cells with a very typical “pince-nez” appearance. Taken together, this study suggests a requirement for further standardization in terms of morphological cell classification, and a need for the development of automatic cell classification–supporting devices for the accurate diagnosis of MDS.