Allelotype of ampulla of Vater cancer: Highly frequent involvement of chromosome 11

Purpose: To determine the genetic differences/similarities in ampulla of Vater cancers (AVC) with respect to other pancreatic tumor types. Methods: We analyzed eight cases of primary AVC by genome-wide allelotyping on DNA obtained from frozen tissue. A total of 372 microsatellite loci were used for each case, for a total of 2,976 microsatellites analyzed. Results: Of the 2,159 informative markers, 400 were allelic losses and 1,759 markers were retained for an average fractional allelic loss of 0.19. Seven cases showed LOH on at least two markers on chromosomal arm 11p, while six cases showed allelic losses on 11q. The high frequency of LOH on chromosome 11 was also confirmed by analysis of an additional 17 paraffin-embedded AVC. Frequent LOH (50% or greater) was also found on chromosome arms 5q, 6q, 9p, 13, 16p, 17p, and 18p. Conclusions: It can be inferred that the targets of inactivation on chromosomes 5q, 9p, and 17p appear to be APC, p16, and p53, respectively, while the critical target(s) of inactivation at the other frequently lost loci remain to be characterized. The resulting allelotype reveals that distinctive chromosomal alterations are present in these neoplasms, indicating that it is a tumor entity distinct from pancreatic adenocarcinoma.