neoplasia

Neoplasia literally means the process of "new growth," and a new growth is called a neoplasm. The term tumor was originally applied to the swelling caused by inflammation.

Neoplasms also may induce swellings, but by long precedent, the non-neoplastic usage of tumor has passed into limbo; thus, the term is now equated with neoplasm. Oncology (Greek oncos = tumor) is the study of tumors or neoplasms.

Cancer is the common term for all malignant tumors. Although the ancient origins of this term are somewhat uncertain, it probably derives from the Latin for crab, cancer-presumably because a cancer "adheres to any part that it seizes upon in an obstinate manner like the crab."

Although all physicians know what they mean when they use the term neoplasm, it has been surprisingly difficult to develop an accurate definition.

The eminent British oncologist Willis has come closest: "A neoplasm 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 cessation of the stimuli which evoked the change."

We know that the persistence of tumors, even after the inciting stimulus is gone, results from heritable genetic alterations that are passed down to the progeny of the tumor cells.

These genetic changes allow excessive and unregulated proliferation that becomes autonomous (independent of physiologic growth stimuli), although tumors generally remain dependent on the host for their nutrition and blood supply.

See also

 Tumors