Neoplasm

Neoplasm (from ancient Greek νεο- neo-, "new" + πλάσμα plasma, "formation", "creation") is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. Prior to neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia. However, metaplasia or dysplasia do not always progress to neoplasia. The growth of neoplastic cells exceeds, and is not coordinated with, that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the stimuli. It usually causes a lump or tumor. Neoplasms may be benign, pre-malignant (carcinoma in situ) or malignant (cancer).

In modern medicine, the term tumor means a neoplasm that has formed a lump. In the past, the term tumor was used differently. Some neoplasms do not cause a lump.