Bone marrow histology.

Bone marrow histology in patient no. 1 prior to imatinib (A,C) and after 6 months on imatinib (B,D). Upper panels are silver stain; lower panels are periodic acid-Schiff stain. Cytogenetic analysis showed 100% Ph⁺ prior to imatinib and 0% Ph⁺ at the time of the follow-up biopsy. Note the increase in reticulin fibers and the marked change in megakaryocyte morphology. Magnification × 20 in all panels.