According to the National Cancer Institute of the government of India, Cancer is the name given to a collection of related diseases where in all its types, some of the body’s cells begin to divide without stopping and spread into surrounding tissues. Cancer can affect any part of the body. When cancer develops, the orderly process of body requiring new cells when the body needs them stops and the old and damaged cells survive when they should die and new cells formed when they are not needed resulting in the formation of tumours.
Cancer is a genetic disease—that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide. Genetic changes that cause cancer can be inherited from our parents. They can also arise during a person’s lifetime as a result of errors that occur as cells divide or because of damage to DNA caused by certain environmental exposures. Cancer-causing environmental exposures include substances, such as the chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun. The process by which cancer cells spread to other parts of the body is called metastasis. Not every change in the body’s tissues is cancer. Some tissue changes may develop into cancer if they are not treated. There are more than 100 types of cancer and each requires diagnosis and care.
Types of cancer are usually named for the organs or tissues where the cancers form. For example, lung cancer starts in cells of the lung, and brain cancer starts in cells of the brain. Cancers also may be described by the type of cell that formed them, such as an epithelial cell or a squamous cell. Examples of some categories of cancers that begin in specific types of cells are Carcinoma, Sarcoma, Leukaemia, Lymphoma, Melanoma, etc.