Background: The aims of the study were to assess the expression of HER2 protein, the amplification of the HER2 gene, and the occurrence of chromosome 17 polysomy in gastric cancer cells and to analyze the relation between the results of such a determination and the selected clinicopathologic parameters in patients treated for gastric cancer.
Methods: Tissue samples of primary tumor from 83 consecutive patients who underwent gastric cancer resection were analyzed by immunohistochemical (IHC) analysis and fluorescence in situ hybridization (FISH).
Results: A positive result of the IHC test, with a minimum score +, was obtained among 22.8% patients. The FISH test was carried out successfully among 58 patients, including 10.3% cases with a positive result, whereas the presence of chromosome 17 polysomy was confirmed among 13.8% patients. A statistically significant dependence was found between the presence of HER2 overexpression and: the lower stage of tumor infiltration, the higher grade of cancer differentiation, no mucinous component, and the intestinal type according to the Lauren classification. Statistically significant relation was found between chromosome 17 polysomy and the tumor location in the proximal part of the stomach, the performance of the palliative procedure, the presence of distant metastases, and a higher frequency of postoperative complications.
Conclusions: There is no complete coincidence in gastric cancer between the occurrence of the HER2 gene amplification and the HER2 receptor expression. The impact of the HER2 gene status and HER2 protein on prognosis in gastric cancer remains unclear. Chromosome 17 polysomy may be an important negative prognostic factor in gastric cancer.