110P - Neoplasia, What is Cancer? Introduction to Neoplasm

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Neoplasia literally means "new growth." A neoplasm, as defined by Willis, is "an abnormal mass of tissue the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after the cessation of the stimuli which evoked the change." Fundamental to the origin of all neoplasms are heritable (genetic) changes that allow excessive and unregulated proliferation that is independent of physiologic growth-regulatory stimuli. Neoplastic cells are said to be transformed because they continue to replicate, apparently oblivious to the regulatory influences that control normal cell growth. Neoplasms therefore enjoy a certain degree of autonomy and more or less steadily increase in size regardless of their local environment and the nutritional status of the host. Their autonomy is by no means complete, however. Some neoplasms require endocrine support, and such dependencies sometimes can be exploited to the disadvantage of the neoplasm. All neoplasms depend on the host for their nutrition and blood supply.