<unk>  is the process by which cells acquire the properties of cancer. This may occur as a primary process in normal tissue, or secondarily as<unk>  degeneration of a previously existing benign tumor.
There are many causes of primary<unk> , or tumorigenesis.  The underlying commonality is genetic mutation either by inheritance or more commonly by acquiring mutations in one's DNA over time.  Although<unk>  may occur because of changes within the cell, it can be induced by inorganic toxic substances such as cadmium or arsenite and organics such as tobacco-specific nitrosamines. It is also thought that some<unk> s are due to viruses such as the Epstein-Barr virus, although this is currently restricted to just a few cancer types.  A more common cancer associated with viral infection is cervical cancer, which has been linked to the human papilloma virus.<unk>  of cells in a benign tumor may be detected by pathologic examination of tissues. Often the clincial signs and symptoms are suggestive of a<unk>  tumor.  The physician, during the medical history examination, can find that there have been changes in size or patient sensation and, upon direct examination, that there has been a change in the lesion itself.
Risk assessments can be done and are known for certain types of benign tumor which are known to undergo<unk> . One of the better known examples of this phenomenon is the progression of a nevus to melanoma.
Malignant transformation
Neoplasia
Benign tumor
Vascular injury
Occult fracture
Congenital abnormality
Spontaneous process
Radiation injury