Bone marrow biopsy findings in a FIP1L1/PDGFRA-positive subject (subject 3). Before imatinib treatment (A), at 1 month following initiation of treatment (B), and at the time of molecular relapse (C). Posttreatment resolution of eosinophilia and hypercellularity was maintained despite molecular relapse. Sections were stained with hematoxylin and eosin (H&E), magnification 400×, and images were obtained by digital microscopy using an Olympus BH-Z microscope (Olympus America, Melville, NY) equipped with a DPlan 40 × 10.65 numeric aperture objective. Images were captured using an Olympus DP12 digital camera system and recorded on a 3.3V Smart Media (SSFDC) card. Imaging software was Adobe Photoshop version 6.0 (Adobe Systems, San Jose, CA).