OBJECTIVE: We sought to describe the CT and MRI features of pure acinar cell carcinoma of the pancreas in adults. MATERIALS AND METHODS: Eleven patients (six women and five men; mean age, 64 years) with acinar cell carcinoma, documented by pathologic examination of resected specimens, underwent CT (n=9) or MRI (n=2) examinations. Two radiologists evaluated imaging studies and determined, by consensus, the following data for each tumor: size, location, margination, internal density or signal intensity, and contrast enhancement pattern. In addition, they assessed the presence of calcification, pancreatic or bile duct dilation, and metastases. Imaging features were correlated with gross and microscopic pathologic features of the tumors. RESULTS: Masses were distributed throughout the pancreas (head, n=5; body, n=2; and tail, n=4). The mean largest dimensions were 6.0 x 5.3 cm (range, from 2 x 1.7 to 15 x 11 cm). Tumors were oval (n=5), round (n=4), or lobular (n=2). Ten (91%) masses were well marginated; nine (82%) were exophytic. Five (45%) masses enhanced homogeneously; the remaining tumors contained cystic areas. All masses enhanced less than the surrounding pancreas. Three (27%) masses contained calcifications. Four (80%) masses invaded the duodenum. Common bile and pancreatic duct dilatation was present in two and three patients, respectively. One patient had metastatic liver disease at presentation. CONCLUSION: Pure acinar cell carcinoma of the pancreas is usually an exophytic, oval or round, well-marginated, and hypovascular mass on CT and MRI. It typically is completely solid when small and contains cystic areas due to necrosis when large.