Unexpected horizontal tumor spread significantly impacts outcomes for patients with oesophagogastric junction (OGJ) cancer, influencing surgical decisions.

• Patients with long pathological margins (δpm > 8mm) and long distal margins (δdm > 3mm) faced worse recurrence-free survival (RFS) and overall survival (OS).
• The long margin group was identified as an independent risk factor for poor RFS and OS.

Intraoperative frozen section analysis can guide additional resections to improve patient outcomes.