Cancer is a word applied to different types of abnormal, unhealthy cells that grow in an uncontrolled way in the body's tissues. Cancer causes malignant tumors (abnormal growths) and loss of normal body organ function. The cancer cells can metastasize (spread) to nearby organs or can spread through the bloodstream or lymph system to other areas of the body, depending on the type of cancer involved and the severity of the disease. In addition to causing changes in and damaging the area where it started, cancer often causes other symptoms, such as fatigue, weight loss, anemia (low blood count), pain, weakness, depression, and shortness of breath, and it can be associated with infection. More than 11 million persons in the United States have cancer. Worldwide, more than 12 million individuals are diagnosed with cancer every year. Health care professionals involved in cancer care include oncologists and hematologists (doctors with specialized education and training in treating cancer and diseases of the bloodstream), surgeons of different specialties including surgical oncologists (who focus on surgical management of cancer), radiation oncologists (doctors with specialized training in using x-ray therapy to treat cancer), and nurses with special expertise in cancer care. The October 13, 2010, issue of JAMA includes an article about cancer screening among patients with advanced cancer. This Patient Page is based on one previously published in the March 17, 2010, issue of JAMA.