Cancer is considered to be one of the leading causes of morbidity and mortality worldwide. Cancer is one of the most serious human health problems. Cancer defined as a malignant tumor, when bnormal cells divide in an uncontrolled way. Cancers may be caused in several ways, namely incorrect diet, genetic predisposition, caused by life style (include cigarette smoking, alcohol, sun exposure, environmental pollutants, infections, stress, obesity, and physical inactivity). Some cancers may eventually spread into other tissues. There are more than 200 different types of cancer.
All cancers begin in cells. Our bodies are made up of more than a hundred million cells. Cancer starts with changes in one cell or a small group of cells. Usually, we have just the right number of each type of cell. This is because cells produce signals to control how much and how often the cells divide. If any of these signals are faulty or missing, cells may start to grow and multiply too much and form a lump called a tumor. A tumor is malignant tumor or benign tumor which has been classified based on the spread of disease. Benign tumors do not spread to other parts of body whereas malignant has high rate of proliferating to other parts. Some types of cancer, called leukemia, start from blood cells. They don’t form solid tumors. Instead, the cancer cells build up in the blood and sometimes the bone marrow.
Cancer is of many types which have been named based on the type of cell affected with. Breast cancer (A cancer that forms in the cells of the breasts). Basal cell cancer (A type of skin cancer that begins in the basal cells). Melanoma cancer (The most serious type of skin cancer). Lung cancer (A cancer that begins in the lungs and most often occurs in people who smoke ). colon cancer(A cancer of the colon or rectum, located at the digestive tract’s lower end). prostate cancer (A cancer in a man’s prostate, a small walnut-sized gland that produces seminal fluid) and lymphoma (A cancer of the lymphatic system). Symptoms vary depending on the type.
Cancer cells have some marked features i.e., they tune out the signals of proliferation and differentiation, they are capable to sustain proliferation, they overcome the apoptosis, and they have power of invasion and angiogenesis. Sequential genetic alterations which produce genetic instabilities accumulate in the cell and a normal cell transforms into a malignant.