Abstract
Gastric carcinoma is second cause of cancer related death worldwide, therefore oncologists urge for identification of new prognostic and predictive markers. HER2 is in gastric cancer negative prognostic factor, associated with increased invasiveness, lymph node metastases and shorter survival, as well as negative predictive marker and target for trastuzumab treatment.
There are two methods of HER2 detection - immunohistochemistry (IHC) and in situ hybridization (ISH). Positivity of HER2 in gastric cancer ranges from 6.8-34% (m. 17.6%) in IHC, and 7.1-42.6% (m. 19.2%) in ISH.
HER2 is more often positive in intestinal type. HER2 detection in gastric carcinoma shows certain specific features - positive cells show either complete or basolateral membranous expression.
Due to more frequent inhomogenity of tumor population, the threshold has been set at 10% of positive cells in resection specimens, but even one cohesive cluster of positive (2+ or 3+) neoplastic cells is sufficient in biopsy.