Cancer is a collective term used for defining class of disease that affects cells of the body. Cells are termed as building blocks of the body. Normally, what happens, after certain point of time old cells of the body die and get replaced with new cells. Sometimes, this process gets disturbed and the situation becomes like this the new cells are growing even when not required and old cells are dying unnecessarily. Those extra new cells form mass on the particular parts of the body, known as tumor. These tumors are known as cancer. Cancer is given the name on the basis on which body part it originates.  For instance, if cancer starts from the lung or breast, it will be termed as lung or breast cancer respectively and so on. The cancer can affect people of any age group, though its risk increases with the age. Some of the alternative names of the cancer are neoplasms, malignancy, carcinoma and tumor.

Cancers are commonly caused due to abnormalities of the transformed cells. These abnormalities may be the outcome of activities like smoking, excessive exposure to any chemical or infectious agent etc.

The prevention the cancer depends upon its cause. If it is caused due to lifestyle related or environmental related factors, it can be prevented easily otherwise it cannot be prevented.