Immunohistochemistry in bone marrow biopsies. Microvessel density (MVD; Nikon Eclipse 80i and Sony DFW-X700 camera, ×400): (A): MVD graded 1 (slightly increased); (B) MVD graded 3 (markedly increased). Vascular endothelial growth factor (VEGF) expression (Olympus BX-51 microscope and DP50 camera, ×600) on bone marrow lymphoplasmacytic cells (LPCs): (C) strong staining on erythrocytes, no staining on LPCs; (D) grade 1 (weak) staining of 10%-50% of LPCs; (E) grade 2 (moderate) staining of more than 50% of LPCs; (F) grade 3 (strong) staining of more than 50% of LPCs. VEGF expression on mast cells: (G) weak staining (+) and (H) moderate staining (++). Because mast cells are rare and scattered compared with LPCs, they have been indicated by a box.