Intraoperative Margin Techniques for Esophagogastric Junction Adenocarcinoma: A Controlled Study

The goal of this clinical trial is to learn if the EndoScell Scanner (ES) imaging system can accurately assess tumor-free surgical margins during surgery for adenocarcinoma of the esophagogastric junction (AEG), compared with standard frozen-section pathology. The main questions it aims to answer are: * Is ES non-inferior to intraoperative frozen-section pathology in identifying positive or negative tumor margins? * Does ES shorten the time needed for margin assessment and reduce the number of additional tissue resections required? Researchers will compare an ES-assisted surgical arm with a conventional frozen-section arm to see if ES improves margin accuracy, shortens operative time, and increases the rate of complete (R0) tumor removal. Participants will * undergo standard AEG resection with randomized assignment to either ES or frozen-section margin checks; * allow collection of margin tissue samples for ES, frozen-section, and final paraffin pathology; * attend routine follow-up visits for up to 2 years to monitor for local recurrence.