11.   Skin cancers commonly occur in people with the rare hereditary disorder, xeroderma pigmentosum, after exposure to sunlight.

12.   Some women have had their breasts removed to avoid the cancer, but even that is not a guarantee because the cancer can occur in the chest wall.

13.   That is because so many skin cancers occur on the head and neck, with one-third of all skin cancers occurring on the nose.

14.   The cancer occurs mainly in men and begins as soft, mole-like purple blotches but can spread to the internal organs or the lymph system.

15.   Women with a family history of breast cancer are most likely to have a mutated BRCA gene if the cancers in their blood relatives occurred before menopause.

16.   Yet even those operations are not a guarantee that cancers will not occur.

17.   Permanent genetic changes that forever increase the risk of lung cancer occurs in teen-agers who smoke, even if they quit later in life.

18.   American Cancer Society epidemiologist Michael Thun urged caution, because in general bladder cancer occurs four times more frequently in men than women.

19.   In the United States, the cancer occurs almost exclusively in people with AIDS.

20.   These cancers often occur because of errors in so-called mismatch repair genes, which look for copying errors that crop up in genes during the production of new cells.