Frequency of HER2 Expression, MMR Deficiency, and PI3KCA Mutation in Pretreated Surgical Specimens of Patients with Esophageal Squamous Cell Carcinoma in Iran Cancer Institute.

Background & Objective: Iran is located in the esophageal cancer geographical belt. As multiple genetic alterations are responsible for the molecular pathogenesis of esophageal squamous cell cancer (ESCC), the role and frequency of HER2 expression, MMR deficiency, and PI3KCA mutation are not well defined. Methods: We carried out HER2/neu expression, dMMR/MSI high, and PI3KCA mutation analysis in specimens of patients with ESCC. We accessed archival tissue blocks related to specimens of 68 ESCC cases at the time of surgery following neoadjuvant chemoradiation. These patients underwent surgery during 2013-2018 at the Cancer Institute of Iran affiliated with the Tehran University of Medical Sciences in Tehran. Results: None of the patients showed HER2 expression, dMMR/MSI high, or PI3K mutations. Conclusion: dMMR/MSI-H and PI3KCA mutation and HER2 expression may not be reliable andfrequent targets for systemic therapy in patients with esophageal SCC.