Significant thrombocytosis in c-Myc^−/− mice. (A) Decreased WBC and hemoglobin concentration but significantly increased platelets in PB of c-Myc^−/− mice. Enlarged platelet size in c-Myc^−/− mice is shown as mean platelet volume (MPV). (B) Significant increase in the absolute number of CD41⁺ megakaryocytes but reduction in Ter119⁺ nucleated erythrocytes in both BM (2 hind limbs) and spleens of c-Myc^−/− mice compared with their age- and gender-matched WT controls. (C-D) PB smears (Wright-Giemsa staining 100×/1.3) show increased platelets in c-Myc^−/− mice. (E-J) Increase in megakaryocyte numbers in c-Myc^−/− BM (F) and spleens (H,J), compared with WT BM (E) and spleens (G,I), as shown by hematoxylin and eosin staining (40×/0.8 air; E-H) and confirmed by megakaryocyte-specific AChE staining (20×/0.7 air) oil (I,J). *P < .05; **P < .01.