Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. There are more than 100 types of cancer, including breast cancer, skin cancer, lung cancer, colon cancer, prostate cancer, and lymphoma. Symptoms vary depending on the type. Cancer treatment may include chemotherapy, radiation, and/or surgery. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body.