These are called the Amsterdam criteria. If these hold true for your family, then you might
want to seek genetic counseling. But even if your family history satisfies the Amsterdam
criteria, it doesn't always mean you have HNPCC. Only about half of families who meet the
Amsterdam criteria have HNPCC. The other half do not, and although their colorectal cancer
rate is about twice as high as normal, it is not as high as that of people with HNPCC. On the
other hand, many families with HNPCC do not meet the Amsterdam criteria.