Discrimination of Unilocular Macrocystic Serous Cystadenoma from Pancreatic Pseudocyst and Mucinous Cystadenoma with CT: Initial Observations

Abstract

To compare the computed tomographic (CT) appearance of pancreatic unilocular macrocystic serous cystadenoma, mucinous cystadenoma, and pseudocyst to determine if there are findings that assist in the differential diagnosis. CT findings in 33 patients (24 women, nine men; age range, 18-84 years; mean age, 41 years) with unilocular pancreatic lesions (macrocystic serous cystadenoma, n = 12; mucinous cystadenoma, n = 11; pseudocyst, n = 10) were retrospectively and jointly reviewed by two blinded observers. Twenty-three patients underwent helical CT, which included pancreatic and portal venous phase imaging with delays of 40 seconds and 65 seconds, respectively, after contrast material injection. Ten patients underwent conventional (nonhelical) CT. The number, size, location, and contour of lesions were reviewed, along with wall thickness and enhancement and other signs of pancreatic and peripancreatic involvement. Diagnosis was based on lesion resection (n = 22) or on a combination of cytologic findings, biochemical markers, and tumor markers (n = 11). The Fisher exact test was used to analyze the results. Three of four CT findings were independently specific for macrocystic serous cystadenoma: location in the pancreatic head, lobulated contour, and absence of wall enhancement. When two of these four criteria were used in combination, 83% (10 of 12) of patients with unilocular macrocystic serous cystadenoma were identified. When three or four of these criteria were used, a specificity of 100% was achieved. Location in the pancreatic head (P <.05), lobulated contour (P <.005), and lack of wall enhancement (P <.005) were specific for macrocystic serous cystadenoma in comparison with mucinous cystic tumor. Lobulated contours (P <.005) were specific for macrocystic serous cystadenoma in comparison with pseudocyst. Other CT findings were not helpful in distinguishing between the three types of lesions. A combination of CT findings is helpful in making the diagnosis of pancreatic unilocular macrocystic serous cystadenoma.