Cancer is a disease in which abnormal malignant body cells uncontrollably grow and multiply. There are many different forms of cancer including carcinomas, sarcomas, lymphomas, leukemias and myeloma.

The body normally regulates the growth, division and death of its cells. When cancer develops, this normal regulation is disrupted and cancer cells continue to grow and divide uncontrollably, forming new abnormal cells. Although some cancers grow rapidly, others do not. The continued, inappropriate growth and lack of normally programmed cell death make a growth malignant. This process creates a mass of tissue known as a tumor or neoplasm. Frequently, cancer cells spread or metastasize from the initial tumor to nearby tissues or organs. Cancer also may spread to distant areas of the body via the bloodstream or the lymphatic system. Although cancer typically forms a tumor, not all tumors are cancerous (malignant). Those tumors that are not malignant are classified as benign. In addition, some cancers, such as leukemia, involve the blood and do not form solid tumors.

Cancer can develop almost anywhere in the body. According to the American Cancer Society (ACS), people in the United States are most often diagnosed with skin cancer (non-melanoma), prostate cancer, breast cancer, lung cancer and colorectal cancer.

Symptoms of cancer vary depending on where it develops and where it has spread in the body. General signs and symptoms include fatigue, unexplained weight changes, fever, pain, or a lump that seems to be growing. However, cancer may not produce any symptoms in its early stages.

According to the ACS, cancer is the second leading cause of death in the United States. However, millions of people are living with cancer or have had the disease. More than 1 million people develop cancer each year, according to the ACS. About one out of every two men and one out of every three women will develop some type of cancer at some point during their lifetime. Although anyone can develop cancer, it is more common in certain age groups and ethnic populations.