A systematic review and meta-analysis of the clinicopathologic characteristics of cystic versus solid pancreatic neuroendocrine neoplasms

Abstract

Cystic pancreatic neuroendocrine neoplasms (PNENs) are rare neoplasms, and presently, it is uncertain whether their behavior is similar or distinct from their solid counterparts. This study aimed to review systematically the present literature to compare the clinicopathologic characteristics of cystic PNENs versus their solid counterparts to determine whether cystic PNENs are likely to be a distinct entity from solid PNENs. Comparative studies of solid versus cystic PNENs studies were reviewed. Cystic and solid PNENs were compared on the basis of several clinicopathologic characteristics. Seven nonrandomized case control studies compared 152 cystic versus 915 solid PNENs. Pooled analysis demonstrated that the likelihood of PNENs to be located in the head/uncinate of the pancreas was lower for cystic than solid neoplasms (27.7% vs 45.5%, odds ratio [OR] 0.452, 95% confidence interval [95% CI] 0.304-0.673, P < .001). Cystic PNENs were less likely to be functional (14% vs 24.4%, OR 0.405, 95% CI 0.221-0.742, P = .003) and were more likely to be benign/uncertain rather than malignant compared with solid PNENs (90.3% vs 65.9%, OR 3.151, 95% CI 1.297-7.652, P = .011). Cystic PNENs were more likely to have a mitotic count <2 per 10 hpf and a Ki67 index <2% (93.3% vs 72.7%, OR 4.897, 95% CI 2.139-11.209, P < .001 and 82.4% vs 54.1%, OR 4.079, 95% CI 2.177-7.641, P < .001), respectively. Cystic neoplasms were also less likely to have regional lymph node metastases than solid neoplasms (11.2% vs 28.9%, OR 0.387, 95% CI 0.219-0.685, P = .001).In this meta-analysis, there was no difference in the 5-year overall survival and 5-year disease-free survival between cystic vs solid PNENs (92.0% vs 86.8%, P .214) and (98.1% vs 83.9%, P = .185). These findings suggest that cystic PNENs tend to be biologically less aggressive compared with their solid counterparts; more data, however, with respect to molecular analysis are required to establish whether cystic and solid PNENs were distinct pathologic entities.