Lymphangiomas with the presence of erythrocytes in mesenteric lymph nodes of Wistar Hannover rats.

We performed morphological and immunohistochemical analyses of erythrocyte-rich vascular proliferative lesions of mesenteric lymph nodes in six male and one female Wistar Hannover rats. These lesions are conventionally diagnosed as hemangiomas due to abundant erythrocytes. Immunostaining was positive for prospero-related homeobox 1 (Prox-1) and/or vascular endothelial growth factor receptor 3 (VEGFR3) in all lesions, suggesting a lymphangitic origin. In 6 of 7 lesions, von Willebrand factor (vWF) immunostaining was negative, suggesting a non-blood vascular origin. These results demonstrated that almost all hemangiomas in rat mesenteric lymph nodes were lymphangiomas. To the best of our knowledge, this is the first report highlighting the lymphatic origin of vascular proliferative lesions in the mesenteric lymph nodes of rats.