Bone marrow trephine specimens showing angiogenesis (CD34 staining) and megakaryocyte c-Mpl grading.

The panels show the following: (A) Microvessel grade 1 (MVG 1) (normal); (B) MVG 1 (RT); (C) MVG 1 (ET); (D) MVG 2 (ET); (E) MVG 3 (ET); (F) MVG 4 (ET); (G) c-Mpl 1 (normal); (H) c-Mpl 1 (RT); (I) c-Mpl 1 (ET); (J) c-Mpl 2 (ET); (K) c-Mpl 3 (ET); and (L) c-Mpl 4 (ET). All images were obtained using light microscopy at × 200 magnification.