Imaging Diagnosis of Cystic Pancreatic Lesions: Pseudocyst versus Nonpseudocyst

Although the clinical, radiologic, and pathologic features of cystic pancreatic lesions are well known, preoperative diagnosis is difficult. Differentiation between a pancreatic pseudocyst and a cystic pancreatic neoplasm is crucial in determining the proper treatment. Careful evaluation of the patient's clinical history is important for accurate diagnosis of a pseudocyst. Clinical scenarios include a pseudocyst developing after acute pancreatitis and a pseudocyst superimposed on chronic pancreatitis. However, a pseudocyst in a patient with no clinical history of pancreatitis poses a diagnostic problem. The differential diagnosis of a neoplastic cystic lesion of the pancreas includes serous cystadenoma, mucinous cystic neoplasms, intraductal papillary mucinous tumor, and solid and papillary epithelial neoplasm. Definitive diagnosis is often possible when the lesion has a typical radiologic appearance, but in many cases characterization with imaging alone is impossible. Thin-section computed tomography with multiplanar reformation, magnetic resonance cholangiopancreatography, and endoscopic ultrasonography have emerged as modalities that can provide additional diagnostic information. Familiarity with the range of imaging appearances and awareness of the diagnostic strengths and limitations of each imaging modality are important for accurate diagnosis and management of cystic pancreatic lesions. © RSNA, 2005