What Is Cancer?
Cancer cannot be classified as a single disease, but rather a group of diseases. In total, more than 100 different types of cancer have been identified. All forms of cancer are characterised by uncontrolled growth and spread of abnormal forms of the body's own cells. The resulting growth is referred to as a 'neoplasm', literally meaning new growth. A neoplastic growth may also be called a tumor and can be benign or malignant.
By definition, benign tumors do not penetrate (invade) adjacent tissue borders, nor do they spread to distant tissues. The spreading process of tumors is called metastasis. Benign tumors remain as localised growths in the area in which they arise. Benign tumors are seldom a threat to life, however, they can grow to such an extent that they interfere with the body's normal functioning. A benign tumor can be removed and usually does not grow back.
In contrast, malignant tumors have the additional property of invading surrounding tissues and metastasising to distant sites. Subpopulations of malignant cells take up residence at the new site, grow anew and again invade.
Generally cancers are named depending on the type of cell or organ in which the cancer cells began. Each form of cancer has a particular pattern of growth and spread. When new tumours develop from the division and spread of cancer cells, the new tumour will have the same cancer cells and cancer name as the first initial tumor. For example, if lung cancer spreads to the liver, the cancer cells in the liver will still remain lung cancer cells. In this situation the disease would be called metastatic lung cancer and would not be called liver cancer.
