An Overview Cancer is a disease that starts with cells growing abnormally. Besides uncontrolled cell growth, malignant tumors also can spread to other sites. This happens when malignant cells invade blood or lymph vessels. When they do, they can spread to a different place in the body. Once they've spread, they can seed and grow into new areas of disease.
Cancer is really many diseases.
All cancers have uncontrolled cell growth and can spread, or metastasize. But, different types are different in how they behave, their ability to spread, what's needed to treat them, and the degree of risk they have. Because they are different, every woman who has breast cancer should think of her disease independently. Her friends or family members may have had a different kind of malignancy .