CEACAM5 and cyst: The patient underwent an endoscopic ultrasound with fine needle aspiration and cyst fluid analysis, demonstrating a Carcinoembryonic Antigen (CEA) level of over 600 ng/mL, an amylase level of over 75,000 U/L, and rare clusters of mucinous epithelium, consistent with a mucinous tumor communicating with the pancreatic ductal system.