Genetic epidemiology of hereditary non-polyposis colorectal cancer syndromes in Modena, Italy: results of a complex segregation analysis.

Complex segregation analysis was conducted in a series of patients with hereditary non-polyposis colorectal cancer (HNPCC) ascertained through probands registered in the Cancer Registry of the Health Care District of Modena in Northern Italy. Altogether there were 71 nuclear families segregating for HNPCC in 28 pedigrees. The analysis favoured the two-loci model, in which the segregation at the major locus is compatible with codominant transmission with a frequency of 0.0044 for the high-risk allele for HNPCC and a lifetime penetrance of 0.728 for heterozygotes.