Pancreatic Cystic Endocrine Tumors: A Different Morphological Entity Associated with a Less Aggressive Behavior.

Background: Cystic pancreatic endocrine tumors (CPETs) are rare lesions and their biological features have been scarcely investigated. Aim: To compare clinical and pathological features of resected non-functioning sporadic CPETs (NF-CPETs) with solid pancreatic endocrine tumors (SPETs) in a single-institution experience. Methods: All patients with a pathologically confirmed diagnosis of sporadic non-functioning pancreatic endocrine tumors who underwent curative resection between 1990 and 2008 were included. A comparison of demographic, clinical and pathological characteristics between CPETs and SPETs was made. Univariate and multivariable analyses were performed to identify preoperative predictors of carcinoma (non-functioning pancreatic endocrine carcinoma). Results: Twenty-one (11.5\%) patients with a histological diagnosis of NF-CPET were identified. The median age was 60 years (IQR 46.5-73.5 years) and a diagnosis of carcinoma (non-functioning pancreatic endocrine carcinoma) was made in 3 (14.3\%) cases. In the comparison with NF-SPETs, no differences were found in terms of gender (p = 0.75), age (p = 0.81), presenting symptoms (p = 0.43), localization of the tumors (p = 0.46) and type of resection (p = 0.31). The incidence of non-functioning pancreatic endocrine carcinoma was significantly lower in the NF-CPET versus the NF-SPET group (14.3 vs. 40.4\%, p = 0.04). By univariate analysis, preoperative predictors of non-functioning pancreatic endocrine carcinoma included the presence of symptoms (OR 3.96, 95\% CI 2.06-7.63) and an increase in the absolute value of radiological diameter (OR 1.05, 95\% CI 1.03-1.07). A cystic morphology of the lesion turned out to be a negative predictor of carcinoma (OR 0.25, 95\% CI 0.70-0.87). These results were confirmed by multivariable analysis. Conclusions: NF-CPETs have a measurable propensity to be benign. In those patients affected by small and asymptomatic NF-CPET a more conservative surgical approach or a follow-up policy could be considered.