Molecular pathogenesis of sporadic duodenal cancer.

Whether duodenal adenocarcinoma should be considered as a gastrointestinal or as a peripancreatic cancer is a matter of debate, as is the opportunity and type of treatment. We investigated 12 such cancers for the genetic anomalies involved in the pathogenesis of gastrointestinal malignancies, including (a) those occurring in common-type cancers - allelic losses at chromosomes 3p, 5q, 17p and 18q, and Ki-ras and p53 alterations; and (b) those characteristic of mutator-phenotype cancers - microsatellite instability and TGF-betaRII gene mutations. We found Ki-ras and p53 mutations in five (42%) and eight cancers (67%), respectively; chromosome 3p, 5q, 17p and 18q allelic losses in two of nine (22%), six of ten (60%), six of nine (67%) and three of ten (30%) informative cancers, respectively. Finally, three cancers (25%) showed widespread microsatellite instability and two of them had a TGF-betaRII gene mutation. Our data suggest that duodenal cancers may arise from either of the two known pathogenetic molecular pathways of gastric and colorectal cancers. The majority of our cases were highly aggressive cancers with frequent chromosomal changes and p53 mutations as observed in the common-type gastrointestinal malignancies, while widespread subtle alterations characteristic of mutator-phenotype cancers occurred in a minority, which also showed a favourable long-term outcome.