Tumorimmunology 2019

Tumor Cells

Tumors arise with great frequency, especially in older animals and humans, but most pose little risk to their host because they are localized and of small size. We call such tumors benign; an example is warts. It is usually apparent when a tumor is benign because it contains cells that closely resemble, and may function like, normal cells. The surface interaction molecules that hold tissues together keep benign tumor cells, like normal cells, localized to appropriate tissues. Circulating tumor cells (CTCs) are cells that have shed into the vasculature from a primary tumor and circulate in the bloodstream. CTCs thus constitute seeds for subsequent growth of additional tumors (metastasis) in vital distant organs, triggering a mechanism that is responsible for the vast majority of cancer-related deaths.