VEGF receptors. VEGFR-1 (Flt-1). Lymphocyte staining was variable and highlighted only a minority of cells in most cases. In the case illustrated in the left panel, many cells in the infiltrate were positive. Very few positive cells were present in the case illustrated in the middle panel. In all cases, granulocytes demonstrated intense cytoplasmic reactivity, scattered erythroid precursors had a predominantly membranous pattern of staining, and megakaryocytes had faint cytoplasmic reactivity. Endothelial cells, which could be identified in most cases, were positive and served as useful internal positive controls. VEGFR-2 (KDR, Flk-1): In most cases, only scattered cells in the infiltrates were positive, with the exception of two cases, one of which is illustrated in the right panel, in which the vast majority of lymphocytes were positive. The microvessel density of these two cases did not markedly differ from the other cases in this group.