Ewing's sarcoma.

There are no known external causes of Ewing’ sarcoma, a form of bone cancer, although a small number of cases are linked to genetic abnormalities. This malignancy occurs with remarkable consistency in registry populations across Europe and the United States, including Los Angeles County. Few cases of it occur after age 30. Although African-Americans and Asian-Americans are at a substantially lower risk than whites or Latinos, there is still a slight tendency toward higher risk among males of lower social class. Despite the racial/ethnic disparity, no systematic pattern of geographical occurrence is apparent, and therefore no local source of causation can be proposed.