HER2 positivity in gastric and esophageal adenocarcinoma: clinicopathological analysis and comparison.

purposePrimary tumor classification of gastric or esophageal cancer has changed significantly with recent alterations of the tumor-node-metastasis (TNM) staging system. Considering these alterations, human epidermal growth factor receptor 2 (HER2) positivity rates were determined and compared in gastric and esophageal adenocarcinoma. Additionally, HER2 positivity in relation to other clinicopathological characteristics was evaluated.

methodsA total of 321 patients with histologically confirmed invasive gastric or esophageal adenocarcinoma were examined for HER2 by immunohistochemy (IHC) and chromogenic in situ hybridization (CISH). IHC 3+ or IHC 2+/CISH-positive tumors were considered HER2 positive. Clinicopathological characteristics were retrospectively retrieved from the patient records.

resultsHER2 positivity was found in 50 of 321 patients (15.6 %). In univariate and multivariate logistic models, HER2 positivity rates were significantly higher in esophageal primary tumors (esophageal 25.0 % vs. gastric 7.4 %) and in intestinal histological tumor type (intestinal 22.6 % vs. diffuse/mixed 5.7 %). No significant differences in HER2 positivity were found between males and females, age below and above 65 years, biopsies and surgical specimens or advanced and early-stage disease. Using the 7th TNM edition, many tumors (30.5 % of all included tumors and 64.5 % of all esophageal primary tumors) previously classified as gastric cancer are now classified as esophageal cancer.

conclusionsHER2 positivity occurs in 15.6 % of invasive gastroesophageal adenocarcinoma in Western patients, of which the majority is esophageal primary tumors and of the intestinal tumor type. With the introduction of the 7th TNM edition, a large number of tumors previously classified as gastric are now classified as esophageal tumors instead, with relatively high HER2 positivity rates in these esophageal primary tumors.