Although much is known about the processes of cancer formation, or carcinogenesis, comparatively little is known about the processes of cancer regression. The former will be explored as an introduction to the latter, and both involve the biological and chemical functions of the body, stated in terms of normal cells vs. cancerous ones. Surgical excision and radiation treatment are excluded from the discussion, though they can be selective if, say, the solid tumor is localized and has not yet spread or metastasized — and if the operations or treatments in themselves do not cause metastasis.