Cancerous tissue can also cause secondary effects, in which the expanding malignant growth puts pressure on surrounding tissue or organs or the cancer cells metastasize and invade other organs. Virtually all organs and tissues are susceptible to cancer. Cancers are usually named for their site of origin. For example, lung cancer that has spread to the brain is called metastatic lung cancer, rather than brain cancer. Carcinoma in situ refers to a cancer that has not spread.
Cancer is the second leading cause of death in the United States.
The incidence of particular cancers varies around the world and sometimes according to ethnic group. For instance, African Americans have comparatively higher cancer rates and cancer mortality rates. It is unclear whether this is due to differences in exposure or to biological susceptibility. The number of diagnosed cases of cancer rose steadily in the United States for decades, but in 1998 it was announced that the number of new cases had begun to decline. Causes of Cancer Cancer results from mutations of certain genes that allow the cells to begin their uncontrolled growth.