ABSTRACT
It is important to remember, in considering neoplasia as defined in this book, that two entities are involved, the host and the neoplasm. Each is independent yet in many ways dependent on the other. The neoplasm is dependent on the host for its blood supply and other supporting tissues, and the host responds to the viability and the nutritional requirements of the neoplasm in the maintenance of the internal milieu of the organism. Weiss (1976) pointed out that the host-tumor relation is quite analogous to the host-parasite relation, which is usually considered in infectious diseases. The tumor-bearing host is confronted with a population of living cells sufficiently independent of the host (relative autonomy) and sufficiently different at the molecular level to warrant designation as parasitic. Yet the analogy of the neoplastic cell to an exogenous parasite is not altogether correct, because in this case the relation to the host is much more subtle, in that the parasitic element is derived from the host’s own tissues.
