Abstract
Collision tumors around the head of the pancreas are extremely rare. The patient was in his sixties who had admitted due to obstructive jaundice. Abdominal CT and MRI showed a pancreatic head mass measuring 3 cm in diameter, with stenosis of the lower bile duct and mild dilatation of the distal main pancreatic duct, suggesting pancreatic head cancer, while ERCP and EUS revealed stenosis and whole-circumferential wall thickening of the lower bile duct, suggesting bile duct cancer. Pre-operative diagnosis was difficult, and the patient underwent pancreaticoduodenectomy. Macroscopically, the tumor was gourd-shaped, suggesting collision tumors. On pathological examination, the tumor was well to poorly differentiated adenocarcinoma and had a direct communication in the narrow part. On immunohistochemistry, it was difficult to confirm the presence of collision tumors. Therefore, flow cytometric DNA ploidy pattern analysis was performed, demonstrating different DNA ploidy patterns between the cancer of the pancreas and that of the bile duct. Consequently, it was concluded that the current case had collision cancers of the pancreatic head and the lower bile duct. To the best of our knowledge, this is the first report of collision tumors of the head of the pancreas and lower bile duct diagnosed by flow cytometric DNA ploidy pattern analysis.
