VASCULAR ARCHITECTURE OF 3-METHYL CHORANTHRENE-INDUCED RAT FIBROSARCOMA DEMONSTRATED BY SCANNING ELECTRON-MICROSCOPY OF RESIN CASTS

A detailed knowledge of the vascular system of tumors is requisite to a clear understanding of tumor physiology and pathology. Accordingly, in this study, examination was made of the vascular architecture of ra t fibrosarcomas induced by 3-methyl choranthrene by scanning electron microscopy of resin casts to observe the three-dimensional vascular pa ttern of the sarcoma. The results were compared with those of correspo nding serial sections of India ink-injected tissue. The major arteries in and around tumors appeared devoid of intra-arterial cushions which regulate blood flow. The arterial lining of resin casts was smooth ju st at the site where it entered the tumor. This may possibly be indica tion of degeneration and loss of the smooth muscle layer in the vascul ar wall. Casts of capillaries were very thin from 4 to 6 mum in diamet er and very few sprouts could be seen. Capillaries, frequently present in superficial regions of the tumor, formed a rich irregular fine pol ygonal network. In fibrous tissue in deeper regions of the tumor, this network was coarse. The absence of intra-arterial cushions and degene ration of muscle cells may thus possibly be the reason for the charact eristic haemodynamics of tumors.