Hereditary non-polyposis colon cancer

Hereditary non-polyposis colon cancer (HNPCC) has been
called Lynch syndrome type I in families where only bowel
cancer is present, and Lynch syndrome type II in families with
bowel cancer and other malignancies. HNPCC is due to
inheritance of autosomal genes that act in a dominant fashion
and accounts for 1–2% of all bowel cancer. In most cases of
bowel cancer, a contribution from other genes of moderate
penetrance, with or without genetic modifiers and
environmental triggers seems the likely cause.