Fig. 1

Summary of stages of leukemogenesis in the same patient. Tissue and cell-block formalin-fixed paraffin embedded (FFPE) sections stained with hematoxylin and eosin (H&E) were visualized by conventional bright-field Kohler illumination light microscopy (Olympus BX40, Japan) with a 20 × Plan achromat objective (Olympus, Japan), 20 × camera mount lens and a DP71 camera (Olympus, Japan). Photomicrographs were obtained after white balancing using the CellSense software (Olympus, Japan). Minor contrast adjustments were performed to the entire image to accurately represent the cells observed in manual microscopy. a Bone marrow biopsy prior to lenalidomide in 2016 at time of accelerated ET, with abnormally increased numbers of megakaryocytes that are atypical with hyperlobation, nucleomegaly and nuclear hyperchromasia and nucleoli with surrounding myeloid and erythroid progenitors. H&E nominal field magnification 400X. b Biopsy of ileocecal mass at time of leukemic transformation in 2018 diagnostic for myeloid sarcoma with sheets of MPO-positive myeloblasts with scant eosinophilic cytoplasm, irregular nuclear contours and prominent nucleoli. H&E nominal field magnification 400x. c Pleural fluid aspirate cytology cell block at time of leukemic transformation in 2018 demonstrates numerous blasts with scant cytoplasm and indistinct nuclear chromatin and surrounding red blood cells. H&E nominal field magnification 400X. Scale bars 50 µm