CT differentiation of solid serous cystadenoma vs endocrine tumor of the pancreas

To differentiate between solid serous cystadenoma (SSCA) and endocrine tumor (ET) of the pancreas using dynamic CT findings.

Between 2001 and 2008, there were 3 SSCA and 15 ET surgically resected in our institute, for whom preoperative multidetector-row CT were available. Various CT features were retrospectively evaluated by two radiologists in consensus for the differentiation between the two entities. Delay time for early and delayed phase images were 40 and 180 or 240s, respectively. For qualitative assessment, density of the tumors relative to the surrounding parenchyma was evaluated, along with other characteristic features. In patients for whom digital data were available, CT values of the tumors were measured, and quantitative assessment was also performed. Relative and absolute washout rate (RWR and AWR, respectively) were also calculated.

Mean sizes of the two groups were similar. Tumors were seen as low density area more frequently in SSCA than in ET on unenhanced CT (3/3 vs 1/14), and also on the delayed phase image (2/3 vs 0/14) (p<0.05). Fibrous capsule was observed more frequently in SSCA (2/3) than in ET (0/14). CT value of the tumor on unenhanced CT was significantly lower, and RWR was higher in SSCA than in ET (p<0.05, Mann-Whitney's U test). The difference in delayed phase CT density and AWR did not reach statistically significant level.

Unenhanced and enhanced CT findings may be of value in differentiation between SSCA and ET.