Mucinous cystic neoplasms of the pancreas: imaging features and diagnostic difficulties

To review the imaging features of mucinous cystic neoplasms (MCNs) of the pancreas and to highlight difficulties in differentiating these lesions from pancreatic pseudocysts.

The imaging investigations, case notes and histopathology of 13 patients who underwent surgery for an MCN of the pancreas, were reviewed.

An erroneous diagnosis of a pancreatic pseudocyst had been made in five of the 13 cases and in two patients cystenterostomy had been performed. Only one patient had a documented history of acute pancreatitis although mildly elevated serum amylase levels were identified in a further five cases. CT and US correctly diagnosed a cystic pancreatic mass in all 13 patients, however cross-sectional imaging features of neoplasia, such as septae, cyst wall calcification, focal thickening of the cyst wall and papillary projections, were absent in five (38%) cases. Coexistent imaging features of chronic pancreatitis were present in five of the 13 patients and in six resected specimens. Cyst wall calcification occurred only in malignant lesions and there was no relationship between cyst size and the degree of malignancy. While ERCP, angiography, and percutaneous needle aspiration may provide additional information, the majority of these examinations were either unhelpful or even misleading.

MCNs of the pancreas are frequently diagnosed and mismanaged as pancreatic pseudocysts with an associated increase in patient morbidity and mortality. Diagnostic imaging can help to distinguish MCNs from pseudocysts when there are features of neoplasia present, however, no imaging investigation can reliably differentiate the two conditions in all cases. If clinical doubt remains, it is preferable to err on the side of safety and either employ a 'wait and watch' strategy or to resect a cystic pancreatic lesion rather than drain a potentially malignant MCN.