Neoplasia

Overview
Neoplasia (new growth in Greek) is abnormal and purposeless proliferation of cells in a tissue or organ. A neoplastic growth is called a neoplasm. Most neoplasms proliferate to form distinct masses, or tumors, but there are also many examples of neoplastic processes which are not grossly apparent, a commonly diagnosed example being cervical intraepithelial neoplasia, a pre-cancerous lesion of the uterine cervix. It is important to note that the term "neoplasm" is not synonymous with cancer, since neoplasms can be either benign or malignant. Leiomyoma (fibroids of the uterus) and melanocytic nevi (moles) are the most common types of neoplasms - both are benign. On the other hand, cancer is a typical example of malignant neoplasia or tumor. Hence, it is important to be able to differentiate between neoplasia, tumor and cancer. Interestingly, there is not a complete consensus in the biomedical community as to the exact biological definition of a neoplasm, although the statement of the British oncologist R.A. Willis is widely cited: 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 stimulus which evoked the change.

Neoplastic tumors often contain more than one type of cell, but their initiation and continued growth is usually dependent on a single population of neoplastic cells. These cells are clonal - that is, they are descended from a single progenitor cell. The neoplastic cells typically bear common genetic or epigenetic abnormalities which are not seen in the non-neoplastic stromal cells and blood-vessel forming cells, whose growth is dependent on molecular stimuli from the neoplastic cells. The demonstration of clonality is now considered by many to be necessary (though not sufficient) to define a cellular proliferation as neoplastic.

Other uses
Neoplasia is also the name of a scientific journal for oncology research or a name of a Computer Demo Group, formed in 1995 (NPL). There is also a movie (Link), inspired by the releases of the demogroup.