When cells multiply without control, the disease cancer is developed. Cancer is one of the leading causes of death in the world. Usually, cells grow and divide only when the body needs them to help keep the body healthy. Sometimes cells keep dividing when new cells are not needed, forming a mass of tissue called a tumor. There are a variety of symptoms, such as: lumps, changes in warts or moles, a sore that will not heal, indigestion, difficulty swallowing, and unexplained changes in weight. Cancer occurs in animals, plants, and humans. …
