ABSTRACT
Cancer is a disease of multicellular organisms whose basis is abnormal, unregulated cell proliferation, often accompanied by abnormal differentiation (neoplasia). Cancers are generally caused by the accumulation of mutations (see below); they are common in higher vertebrates, but many other organisms do not manifest cancer because they do not live long enough. Cancer is well studied in animals, but tumors also occur in plants (q.v. crown gall disease).
