Abstract
Background. It has been hypothesized that in some but not all families with hereditary nonpolyposis colorectal cancer (HNPCC) there is a high risk of certain cancers other than colon cancer. Methods. The authors compared the observed frequency of cancer at specific sites in more than 1300 high-risk members of 23 kindreds with HNPCC with expectations based on general population incidence and evaluated the hypothesis that there was heterogeneity in cancer frequency among families. Results. The authors observed significantly increased numbers of cancers of the stomach, small intestine, upper urologic tract (renal pelvis and ureter), and ovary. No excess was seen in other cancer types that have been associated previously with HNPCC, including cancer of the breast, pancreas, and urinary bladder. Significant heterogeneity among families was observed in the frequencies of endometrial, ovarian, and upper urologic system cancer. Conclusion. In addition to early onset cancers of the colorectum, HNPCC family members are at increased risk for cancers of other gastrointestinal tract organs, and, especially in some families, cancers of the upper urologic and female genital tract.