Uncommon tumors and pseudotumoral lesions of the pancreas.

Ductal adenocarcinoma is the most common tumor of the pancreas, accounting for about 80% of all pancreatic tumors. The other 20% of pancreatic tumors is represented by a heterogeneous group of pancreatic neoplasms that includes cystic pancreatic neoplasms, islet cell tumors, and the so-called rare pancreatic tumors. In addition, the pancreatic gland may present a variety of inflammatory and pseudotumoral lesions that may mimic a primary pancreatic neoplasm. These uncommon tumors and pseudotumoral lesions present a wide spectrum of imaging findings and they are often poorly understood by the radiologist, becoming a diagnostic challenge. Some of these lesions may show an appearance similar to ductal adenocarcinoma being radiologically indistinguishable. However, some of these lesions sometimes may present specific features on imaging studies that may help to characterize the mass and to suggest a correct diagnosis. Many of these uncommon tumors and pseudotumoral lesions have a different approach, therapy, and prognosis than ductal adenocarcinoma. Therefore, it is important for the radiologist to be familiar with these entities to include them in the differential diagnosis to initiate an appropriate lesion-specific workup and treatment. In the present article, we review the radiological features of uncommon pancreatic tumors, atypical manifestations of ductal adenocarcinoma, and pseudotumoral masses, focusing on those features that can be helpful for the differential diagnosis.