Bone marrow angiogenesis and myelofibrosis after first-line imatinib therapy of chronic-phase Ph⁺/BCR-ABL⁺CML. (A-C) CD34 immunostaining. (D-E) Gomori silver impregnation. Original magnification, × 180 (A-B,D) and × 380 (C,E). (A) Pretreatment bone marrow biopsies reveal a significantly increased number of microvessels with enhanced tortuosity and branching. (B-C) Following imatinib treatment, a remarkable reduction of vascularity (B) accompanied by increased vascular roundness and decreased tortuosity of microvessels (C) is observable. These findings are generally associated with a reduction of the fiber content and occurrence of cytogenetic response. (D) Pretreatment biopsy. (E) Biopsy 8 months after imatinib treatment.