Osteoclast-like Giant Cell-type Pancreatic Anaplastic Carcinoma Presenting with a Duodenal Polypoid Lesion.

Osteoclast-like giant cell-type (OCGC) anaplastic carcinoma is a rare variant of pancreatic ductal adenocarcinoma, and its imaging characteristics and progression pattern have not been fully clarified. The patient was a 73-year-old man who had been incidentally found to have a pancreatic head tumor. Computed tomography demonstrated a 3-cm marginally enhanced mass at the pancreatic head, continuing toward the duodenum. Diffusion-weighted magnetic resonance imaging showed a retained diffusion capacity. Duodenoscopy revealed a 1.5-cm polypoid lesion, covered by a dirty coat, near the major papilla. Surgical material revealed OCGC pancreatic anaplastic carcinoma protruding to the duodenum, accompanied by multiple hemorrhagic foci and hemosiderin precipitations.