The clinical significance of tumor spread has always been appreciated. Yet, in spite of the pioneering work and outstanding contributions of investigators such as D. Coman, H. Green, B. Fisher, S. Wood and I. Zeidman, studies on metastasis rarely achieved the popularity afforded to more esoteric areas of tumor biology. Tumor dissemination, occurring as it does in a responding host and being composed of a series of dynamic int ractions, is a highly complex phenomenon. Few investigators were brave enough to attempt to unravel the mechanisms involved. Paradoxically, this very complexity may have...