Clinicopathologic Characteristics and Long-term Outcomes of Cystic Versus Solid Pancreatic Neuroendocrine Tumors: A...

To investigate the clinicopathologic features and long-term outcomes of cystic and solid pancreatic neuroendocrine tumors (PanNETs).

PanNETs uncommonly present as cystic lesions. Whether cystic PanNETs represent a distinct clinical entity compared with solid PanNETs is controversial.

Clinicopathologic data of patients with resected PanNETs were collected from 4 high-volume centers between 2000 and 2019. Clinicopathologic characteristics and outcomes of patients with cystic and solid PanNETs were compared based on a 3 cm tumor size cutoff using the χ 2 test and Mann-Whitney U test. Survival estimates were calculated with the Kaplan-Meier method and log-rank test and multivariable analysis using a Cox proportional hazard model.

Of the 1727 patients undergoing pancreatectomy for PanNET, the median age was 58.1 years (IQR: 18.4), and 53.3% were males. Of these, 177 (10.3%) were cystic, and 1550 (89.7%) were solid. Cystic PanNETs were more prevalent in patients with hereditary syndromes, less frequently functional, and more often located in the body/tail of the pancreas. After the exclusion of patients with functional tumors, World Health Organization G3 tumors, hereditary syndromes, neoadjuvant treatment, and metastatic stage, 145 cystic PanNETs were compared with 1059 solid PanNETs, and the median follow-up period of the cohort was 64 months. Cystic PanNETs demonstrated significantly fewer high-risk histopathologic features, lymph node (LN) metastases (5.5% vs 24.0%, P < 0.001), and distant recurrence (4.1% vs 14.4%; P < 0.001). Among tumors, ≤3 cm, cystic PanNETs had a low rate of LN metastases (3.9% vs 17.8%; P < 0.001), recurrence (3.1% vs 8.4%; P = 0.041), and low propensity to recur distantly. Cystic PanNETs had favorable long-term survival regardless of tumor size.

Cystic PanNETs have a more benign course than their solid counterparts, and conservative management can be considered for endoscopic ultrasound-guided fine needle aspiration-proven cystic PanNETs ≤3 cm. Parenchyma and LN-sparing resections are warranted in patients with cystic PanNETs >3 cm. Patients with poor baseline performance status may forego cystic PanNET resection and not affect their overall survival.