IMiD therapy spares megakaryocytes in the bone marrow. (A) Bone marrow aspirates before and during treatment from case 1 listed in Table 1 (May-Giemsa staining). Lower panels show representative megakaryocytes. Images were captured by a BH-2 microscope (Olympus) and ACT-2U imaging software (Nikon) with ×100 (upper; scale bar, 100 µm) and ×400 (lower; scale bar, 25 µm) magnification. (B) Number of megakaryocytes per 50 low-power fields (LPFs) in bone marrow aspirates from 24 patients listed in Table 1. Each line represents the change in the number of megakaryocytes in each patient. P value was determined by 2-tailed Student t test. To avoid the potential influence of tumor infiltration on hematopoiesis, bone marrow samples with <10% clonal plasma cells were examined.