Fig. 1

Histologic and immunohistochemical characteristics of case 1. (Top left): the architecture of the lesion was diffuse with areas of prominent sclerosis (asterisk). Large vessels (arrow) were observed at the periphery. (Upper middle left): the lesion was formed by small irregular angiomatous spaces with anastomosing pattern, lined by a simple layer of endothelial cells, some with hobnail morphology. (Lower middle left): prominent chronic inflammation accompanied by inter-tubular fibrosis and glomerular sclerosis was observed at the lesion margins (highlighted by histochemical Masson’s trichrome and Gomori’s reticulin staining in lower left). (Top right): endothelial cells were CD34-positive and bordered by HHF-35-positive pericytes (upper middle right). (Lower middle right): proliferation index (Ki67) was low, around 2–3% highlighting endothelial cells with enlarged nuclei (arrowhead). (Bottom right): Increased number of CD20+ B and CD8+ T lymphocytes (as well as CD4+ T-cells-not shown), but not plasma cells were observed all over the lesion. (3,3′ diaminobenzidine as chromogen, hematoxylin as counterstain, original magnifications 40X, 100X, 400X)