Non-Polyposis Syndromes
Hereditary non-polyposis colorectal cancer (HNPCC)
When mismatch repair gene mutations were first identified as the cause of non-polyposis hereditary colorectal cancers (HNPCC), it was thought that they would be responsible for the great majority of cases fulfilling clinical criteria of HNPCC. The reality is more complex. We know at least half of the families fulfilling Amsterdam criteria of HNPCC actually do not have alterations in the MMR system and, therefore, other genes are likely responsible for this syndrome. Thus, HNPCC is a wide term that includes Lynch syndrome (caused by inherited MMR genes), and at least another group of inherited cancers of a yet unknown cause. The latter group, as a whole, also presents distinct clinical features from Lynch syndrome tumors: these patients present mostly left-sided tumors without lymphocytic infiltrate; cancers usually present at a latter age, though still much earlier that sporadic colorectal cancers; penetrance is lower; and more often fulfill Amsterdam II criteria 1 . Other authors have reported a subset of families fulfilling Amsterdam I clinical criteria for HNPCC but without MMR deficiency. This group presented a lower incidence of colorectal cancer than the group with Lynch syndrome but no increased incidence of other cancers.
Click here for a bibliography of references.
