The Generation of the Metastatic Phenotype

It is now a well-worn adage, almost a cliche in cancer research circles, that the process of cancer metastasis is an inefficient process. Primary tumours may release millions of cells into the vascular system and yet a very small proportion, estimated at about 0.01%, can successfully form distant metastases. There has been some debate as to whether cells with metasta-sising ability pre-exist in a neoplasm and hence their dissemination to distant sites is a non-random process or whether, as Weiss (1983) has argued, most cancer cells have the ability to metastasise and that they randomly enter a ‘transient metastatic’ compartment which increases their chances of negotiating the multiple hurdles of the metastatic cascade.