Structure of the 21 morphological classes of BM cells used in this study. (A) Ordering of the classes into hematopoietic lineages. In agreement with routine practice, major physiological classes of myelopoiesis and lymphopoiesis are included, as well as characteristic pathological classes and classes for artefacts and unclear objects. As detailed in the main text, all cells were stained using the May-Grünwald-Giemsa/Pappenheim stain, and imaged at ×40 magnification. (B) Distribution of the 171 374 nonoverlapping images of our data set into the classes used.