Vascularization in infantile brain tumors induced by human adenovirus type 12 in rats

Early vascular changes in the undifferentiated infantile brain tumors induced by human adenovirus type 12 (Ad 12) in rats were studied using the India ink injection method, scanning electron microscopy (SEM) of vascular corrosion casts, transmission electron microscopy, and the peroxidase anti peroxidase method for glial fibrillary acidic protein detection. The process of vascularization of solid type tumors was divided into five phases: Stage O, no remarkable changes; Stage I, dilatation of vessels; Stage II, formation of vascular network; Stage III, fine branching in the vascular network; and Stage IV, necrosis. SEM of vascular replica in Stage III suggested compression of the vessels by proliferating tumor cells. In the tapetum region, Stage I was recognized in solid type tumors 100 to 230 (m = 180) micrometer in diameter, while in the olfactory lobes and in the anterior horn of lateral ventricle closely adjacent to the vascular gray matter, Stage I occurred in much larger tumors. In the diffuse type tumors, the dilatation of vessels was first noticed when the tumors were about 1600 micrometers in diameter. The solid type tumors mainly developed in the poorly vascular subventricular zone, while the diffuse type ones were usually found deep in the vascular gray matter. The results indicate that vascularization is closely related to the local vascularity and the growth pattern of the microtumors, and that of the solid type tumors induced by Ad 12 may be a model of vascular changes in infantile brain tumors which mostly develop and grow rapidly in the subventricular zone which have poor vascular development.