Gastric cancer is the fifth most common cancer, and the fourth leading cause of death, worldwide. Human epidermal growth factor receptor 2 (HER2) expression in gastric cancer has been associated with progressive disease, poor response to chemotherapy, and poor prognosis. Trastuzumab is an anti-HER2 monoclonal antibody. It is now recommended in combination with chemotherapy as a new standard therapeutic option for patients with HER₂-positive advanced cancer of stomach and gastroesophageal junctions. There is no data regarding HER₂ protein expression in Algerian gastric cancer tissues.

In this retrospective study, we evaluated the prevalence of HER₂ overexpression in gastric cancer through medical records from 2019 to 2022. Clinicopathological features were assessed in patients with adenocarcinoma gastric cancer. Most patients aged 30 to 78 years were men (60%), 32% were older than 60 years. Patients were diagnosed at pTNM stages I, II and III (26.5% and 26.5% and 47%, respectively). Thirty-four (34) gastric tissues were stained and evaluated for HER2 overexpression by immunohistochemistry. Four patients (12%) showed overexpression (score 3+), 10/34 (29%) had negative (Score 0-1) and 20/34 (59%) had equivocal staining (Score 2+). There was no association between HER2 overexpression and age (p=0.102) or sex (p=0.23). HER2 overexpression was highest in well and moderately differentiated tumors (p=0.0093).

The determination of HER2 status in GC is important for their association with specific clinicopathological features and for their prognostic and predictive value.