Cancer is a term used for diseases in which abnormal cells divide without control and are able to spread and invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems. If uncontrolled, cancer can result in death. All cancers begin in cells, the body’s basic unit of life. The body is made up of many types of cells. These cells generally grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells. However, sometimes this orderly process goes astray. The genetic material of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumor. Not all tumors are cancerous; tumors can be benign (non-cancerous) or malignant (cancerous). Some cancers do not form tumors. For example, leukemia is a cancer of the bone marrow and blood.
Most cancers are named for the organ or type of cell in which they start. Cancers fall into various categories, including: sarcoma (cancer beginning in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue); carcinoma (cancer beginning in the skin or in tissues that line or cover internal organs); and blood cancers.
More is known about the cause of some forms of cancer than others. In general, cancer is caused by both external factors (e.g., tobacco, infectious organisms, chemicals, and radiation) and internal factors (e.g., inherited mutations, hormones, immune conditions, and mutations that occur from metabolism). These causal factors may act together or in sequence to initiate or promote the development of cancer. Often the amount or dosage of exposure is an important determinant and sometimes there can be a long latency period of years or even decades between exposure to external factors and detectable cancer. Asbestos exposure and mesothelioma is a good example of a cancer that can take decades to cause symptoms. The immune system response is fundamentally important.
Cancer Facts & Figures 2012 from the American Cancer Society provides some good insights into the scope and magnitude of these diseases collectively referred to as cancer. Approximately 1,638,900 new cases of cancer were expected to be diagnosed in 2012 and this figure does not include carcinoma in situ (non-invasive cancer) of any site except the bladder and does not include basal and squamous cell skin cancers. More than 1 million basal and squamous cell skin cancers were expected to be diagnosed. Approximately 577,190 Americans are expected to die of cancer, more than 1,500 people a day, in 2012. Cancer is the second most common cause of death (only heart disease kills more), accounting for 1 in 4 deaths. Cancer will be the leading cause of death in the United States within a few years. The 5-year survival rate for all cancers diagnosed between 2001 and 2007 is approximately 67%, as compared to 49% during the 1975-1977 period. It is important to note that this does not reflect recent treatment and detection improvements. Cancer can impact a person at any age, but 77% of all cancers are diagnosed in people 55 and older. Childhood cancers represent less than 1% of all new cancers diagnosed, but cancer is the second leading cause of death in children (only accidents kill more children than cancer). There are an estimated 58,500 cancer survivors age 0 to 14 and an additional 12,000 are expected to be diagnosed in 2012.
One in two men in American will get cancer during their lifetime and more than one in three women will get cancer in their lifetime. The National Cancer Institute estimates that over 13.7 million Americans with a history of cancer were alive in January 2012. Some were cancer-free, others were not. The number is expected to increase to 18 million by January 2022.
As contrasted with “solid tumors,” blood cancers are cancers of the blood and lymph systems. There are three categories of blood cancer: lymphoma, leukemia, and myeloma. Blood cancers are prevalent. Every four minutes someone in America is diagnosed with blood cancer and someone dies from the disease every 10 minutes. Over 138,000 Americans are diagnosed annually with blood cancer, accounting for approximately 9 percent of new cancer cases diagnosed in the United States and 9.5% of the cancer deaths. Blood cancer is the most common form of cancer in children, with leukemia causing more deaths in children and young adults under the age of twenty than any other cancer. Leukemia, lymphoma, and myeloma cause more than 54,000 deaths per year in the United States. It is estimated that more than 957,000 Americans are living with blood cancer. www.seer.cancer.gov (published on June 30, 2010).
