Abstract

There axe four mechanisms of the dissemination of cancer: direct extension by tissue planes, by lymphatics, by the vascular system, and by implantation. Implantation may be either spontaneous or iatrogenic, and the unique cases of spontaneous implantation reported by Beahrs, in which carcinoma of the colon had seeded a fresh hemorrhoidectomy wound, illustrate how hardy cancer cells can be. The factors affecting the spread of cancer appear even more important than the mechanisms themselves. Immunologic factors (including stimulation), immunosuppression, tumor enhancement, tumor inhibition, and contrasting features are important. Stimulation of the immune process is becoming important because so many chemicals or processes are immunosuppressive, and it is now evident that all, or practically all, major operations are immunosuppressive. Accordingly, at the time of operation for cancer the patient should be given something to stimulate his immune system during the three or four weeks it is being suppressed by the operation.