Pharmacodynamic effects of imatinib. *Antiphosphorylated PDGFRA staining (original magnification × 400) before (A) and after (B) imatinib treatment (patient 1) and *antiphosphorylated PDGFRB staining (original magnification × 400) before (C) and after (D) imatinib treatment (patient 11). Microscope: Olympus BX45; camera: Olympus DP25; acquisition software: CellSens Standard (Olympus).