Representative pattern of immunohistochemical staining of normal marrow for VEGF, FLT-1/VEGFR-1, and KDR/VEGFR-2.

(upper left) Hematoxylin and eosin staining. (upper right) Faint VEGF signal in megakaryocytes, monocytes, and occasional myelocytes. (lower left) Low-intensity Flt-1/VEGFR-1 signal in macrophages–histiocytes and rare myeloid elements. (lower right) Strong KDR/VEGFR-2 staining in scattered histiocytes (1000 × magnification).