Editing Neoplasm (section)

===Clonality===
Neoplastic tumors are often [[Tumour heterogeneity|heterogeneous]] and contain more than one type of cell, but their initiation and continued growth are usually dependent on a single population of neoplastic cells. These cells are presumed to be [[Monoclonality|monoclonal]] – that is, they are derived from the same cell,<ref>{{Cite web|url=http://www.medterms.com/script/main/art.asp?articlekey=2754|title=Medical Definition of Clone|access-date=2015-02-10|archive-date=2012-10-25|archive-url=https://web.archive.org/web/20121025074001/http://www.medterms.com/script/main/art.asp?articlekey=2754|url-status=dead}}</ref> and all carry the same [[mutation|genetic]] or [[epigenetics|epigenetic]] anomaly – evident of clonality. For lymphoid neoplasms, e.g. [[lymphoma]] and [[leukemia]], clonality is proven by the amplification of a single rearrangement of their [[immunoglobulin]] gene (for [[B cell]] lesions) or [[T cell receptor]] gene (for [[T cell]] lesions). The demonstration of clonality is now considered to be necessary to identify a lymphoid cell proliferation as neoplastic.<ref name="pmid7990861">{{cite journal |vauthors=Lee ES, Locker J, Nalesnik M, Reyes J, Jaffe R, Alashari M, Nour B, Tzakis A, Dickman PS | title = The association of Epstein-Barr virus with smooth-muscle tumors occurring after organ transplantation | journal = N. Engl. J. Med. | volume = 332 | issue = 1 | pages = 19–25 |date=January 1995 | pmid = 7990861 | doi = 10.1056/NEJM199501053320104 | doi-access = free }}</ref>