Pancreatic groove cancer with large cystic lesion.

Groove pancreatic cancer is a malignant tumor that originates from the groove between the pancreas, duodenum, and bile duct. Groove pancreatic cancer shares similarities with groove pancreatitis in terms of clinical symptoms and imaging findings, which often makes it difficult to distinguish between the two diseases. We describe the case of a patient with a cystic lesion associated with groove pancreatic cancer. A 54-year-old male patient presented with sudden vomiting, hematemesis, and persistent epigastric pain. Enhanced computed tomography revealed a hypoenhanced, ill-defined lesion extending from the pancreatic head to the duodenum, with a large duodenal cystic formation. Despite various diagnostic efforts, a definitive diagnosis of malignancy before surgery remained elusive. Intraoperative findings revealed that the tumor was resectable. Subtotal stomach-preserving pancreaticoduodenectomy with portal vein resection and right hemicolectomy were performed. The resected specimen revealed groove pancreatic adenocarcinoma invading the duodenum and ascending colon. A large cyst was observed within the duodenal wall, the interior of which was lined with cancer cells. Despite postoperative chemotherapy, the patient succumbed to the disease 17 months after resection. This case emphasizes that when a groove area lesion with a huge paraduodenal cyst is observed, the possibility of groove pancreatic cancer should be considered.