Primary Pancreatic Yolk Sac Tumor Presenting as Diffusely Enlarged Pancreas in Initial 18F-FDG PET/CT.

Yolk sac tumor is a rare and highly malignant germ cell tumor. We report a case of yolk sac tumor primarily in the pancreas in a 32-year-old man. He presented with pancreatitis at presentation with significantly increased serum alpha-fetoprotein (AFP). F-FDG PET/CT revealed diffuse enlargement of the pancreas in the neck, body, and tail portion with homogeneously increased FDG uptake, similar to the change of pancreatitis. The lesion progressively developed to a huge pancreatic mass in the follow-up images, and endoscopic ultrasonography-guided aspiration biopsy of the pancreatic mass confirmed the diagnosis of yolk sac tumor.