[Why do tumor cells avoid immune surveillance?]

Why does cancer develop? What is the essence of premalignant lesions? My answer to these sacramental questions follows. I found out that hyperplastic and tumor nodules are immunologically privileged sites, like the anterior chamber of the eye or the hamster's retrobuccal sac. The antigens from the nodules do not provoke the body's immune reactions, unlike the same antigens from the extranodular tissue. On the other hand, both the autoantibodies and the killer-cells sensitized to this antigens are unable to react with that part of the cells possessing antigens, which are situated within the nodules and completely destroy the same cells in the extranodular tissue. Hyperplastic and tumor nodules are special sites where immunological surveillance is absent. It is because they have no lymphatic and so recirculation of immunocompetent cells through its territory is impossible. Thus, newborn malignant cells in these precancerous formations avoid the immunological control and survive, in contrast to the tissue with the normal structure. So, neoplastic processes will be free from immunological surveillance in the precancerous sites and will therefore be more likely to progress.