Manifestations of hereditary colorectal cancer.

Seven families with hereditary colorectal cancer syndromes are presented. Four are of the nonpolyposis type, two with polyposis, and one with a mixed pattern. We have observed an early onset of hereditary colorectal cancer, the nonpolyposis type of which manifests itself mostly in the proximal colon, whereas the syndrome with polyposis manifests itself in the distal colon. In addition, the rest of the gastrointestinal tract may be involved. Therefore surveillance endoscopies in affected families should be started at least 20 years earlier than usual.