Fig. 1

Bone marrow at presentation (MDS) and skin lesions after transformation (BPDCN). Photomicrographs of bone marrow core biopsy specimens at presentation show a erythroid-predominant trilineage hematopoiesis and dysplastic megakaryopoiesis with an increased number of small monolobated megakaryocytes (H&E ×400), and b megakaryocytes with widely separated nuclear lobes (Giemsa, ×1000). c Photographs show violaceous plaques on the abdomen at BPDCN diagnosis, including a truncal skin lesion on the central abdomen demarcated with blue ink, enlarged for inset. Photomicrographs of skin biopsy of the abdominal lesion showing d extensive dermal infiltrate of immature-appearing mononuclear cells (H&E ×40), and e infiltrate that is uniformly and strongly positive for CD123 (immunohistochemistry with hematoxylin counterstain, ×20). f Photograph of same abdominal area showing resolving lesions after 1 month of CD123-targeted therapy with SL-401