Epidemiologic and genetic factor in colorectal cancer: development of cancer in dizygotic twins in a family with Lynch syndrome

Human tumours usually develop due to a close inter action between environme ntal and genetic factors. This concept applies also to well defined genetic diseases such as Hereditary Nonpolyposis Colorectal Cancer (HNPCC or Lynch syndrome), which is featured by early onset tumours of the large bowel(and other target organs), striking aggregation of neoplasms in families, and v ertical transmission consistent with an autosomal dominant pattern of inher itance. As a further example of gene/environment interaction, we report on a Hereditary Nonpolyposis Colorectal Cancer family in which two dizygotic t wins were affected by cancer of the large bowel. One of the twins was sligh tly overweight and showed many common risk factors for colorectal carcinoma he developed a Dukes' C lesion at the age of 52 The other twin was not ove rweight and was much less exposed to exogenous risk factors; a Dukes' B car cinoma was diagnosed nt age 60 during a control endoscopy. This anedoctal r eport suggests that diet and lifestyle are of relevance also in patients wi th genetically determined tumours of the large bowel. It follows that the c ontrol of these environmental factors might be associated with a delay of t umour occurrence and possibly with a less aggressive tumour behaviour.