MYC insertions in diffuse-type gastric adenocarcinoma.

Background: MYC is important in gastric carcinogenesis. A few studies reported MYC translocation or insertion associated with gastric cancer. Materials and Methods: MYC copy number and its insertion, as well as the chromosomes in which MYC was inserted, were evaluated by fluorescence in situ hybridization assay in interphase and metaphase cells of 12 diffuse-type gastric cancer samples. MYC protein expression was evaluated by immunohistochemistry. Results: The presence of 3 MYC signals was the most frequent alteration. All cases also presented 4 and 5 MYC signals. In all samples, we observed chromosome 8 trisomy with MYC copies and MYC insertion into the chromosomes 2, 7, 14, 17, 18 and 22. All samples presented nucleic and cytoplasmic immunoreactivity. Conclusion: MYC cytoplasmic immunoreactivity can be the result of MYC insertion with the breakpoints within or close to the regions that are able to target the nucleus. MYC insertion and cytoplasmatic immunoreactivity may be a common characteristic of diffuse-type gastric cancer.