Six primary cancers in individuals. Report of four cases.

Four patients who had six or more primary cancers are described in this article. Two of the patients had seven cancers each; the most frequent cancer site was the colon. These patients were young at the onset of their first cancer and had a long survival. All the patients had a strong family history of cancer, especially colon cancer. We found that family members of individuals with multiple cancers should be considered to have an increased risk for the development of cancer.