Razi Journal of Medical Sciences

More than two decades ago, Henry T. Lynch reported a hereditary non polyposis colorectal cancer (HNPCC) which is seen in some families with dominant mode of inheritance, also know as Lynch Syndrome type I and II. This form to hereditary colorectal cancer has an early age of onset (Less than 45 years) with predominantly proximal colonic involvement (type I) and can also be associated with extracolonic cancer (type II). It is estimated that perhaps 4% - 13% of all cases of colorectal cancer are attributable to HNPCC. In this article, six cases of Cecal and / or ascending colon carcinoma are presented which are site-specific with a young age of onset, and one out of two of these patients are close relatives such as:

brother and sister, mother and son and nephew and uncle, although for final Confirmation we need chromosome studies on these three families, but these could be considered clinically as Lynch 1- Syndrome pathology of most of these cases is of mucin-producing type adenocarcinoma.

It is concluded that, because of a high incidence of colonic carcinoma with a young age of onset (perhaps around 50%) in Iran, the incidence of HNPCC could be much higher than in western populations.