Reappraisal of a 2-Cm Cut-off Size for the Management of Cystic Pancreatic Neuroendocrine Neoplasms

Abstract

Objective: The aim of this study was to characterize an international cohort of resected cystic pancreatic neuroendocrine neoplasms (cPanNENs) and identify preoperative predictors of aggressive behavior. Background: The characteristics of cPanNENs are unknown and their clinical management remains unclear. An observational strategy for asymptomatic cPanNENs ≤2 cm has been proposed by recent guidelines, but evidence is scarce and limited to single-institutional series. Methods: Resected cPanNENs (1995–2017) from 16 institutions worldwide were included. Solid lesions (>50% solid component), functional tumors, and MEN-1 patients were excluded. Aggressiveness was defined as lymph node (LN) involvement, G3 grading, distant metastases, and/or recurrence. Results: Overall, 263 resected cPanNENs were included, among which 177 (63.5%) were >2 cm preoperatively. A preoperative diagnosis of cPanNEN was established in 162 cases (61.6%) and was more frequent when patients underwent endoscopic ultrasound [EUS, odds ratio (OR) 2.69, 95% confidence interval (CI) 1.52–4.77] and somatostatin-receptor imaging (OR 3.681, 95% CI 1.809–7.490), and for those managed in specialized institutions (OR 3.12, 95% CI 1.57–6.21). Forty-one cPanNENs (15.6%) were considered aggressive. In the whole cohort, LN involvement on imaging, age >65 years, preoperative size >2 cm, and pancreatic duct dilation were independently associated with aggressive behavior. In asymptomatic patients, older age and a preoperative size >2 cm remained independently associated with aggressiveness. Only 1 of 61 asymptomatic cPanNENs ≤2 cm displayed an aggressive behavior. Conclusions: The diagnostic accuracy of cPanNENs is increased by the use of EUS and somatostatin-receptor imaging and is higher in specialized institutions. Preoperative size >2 cm is independently associated with aggressive behavior. Consequently, a watch-and-wait policy for sporadic asymptomatic cPanNENs ≤2 cm seems justified and safe for most patients.

Clinical relevance of performing endoscopic ultrasound‐guided fine‐needle biopsy for pancreatic neuroendocrine tumors less than 2 cm

“…incidence of recurrence. [29][30][31] While the overall incidence of recurrence was low, pNETs less than 2 cm with moderate/poor differentiation or Ki-67 index more than 3% still have malignant potential, regardless of small tumor size. 17 In particular, pNETs with a high…”

Primary hepatic neuroendocrine neoplasms: imaging characteristics and misdiagnosis analysis

“…The presence of surrounding cystic/necrotic areas observed in this study remains unexplained by the current theory. Based on the pathological findings from a previous investigation on pancreatic NENs ( 27 ), it is postulated that internal hemorrhage/necrosis within tumors contributes to the formation of cystic foci as visualized through imaging techniques. Certainly, two patients in this cohort exhibited a centrally distributed area of low attenuation, potentially attributed to tumor necrosis.…”

Consensus of clinical diagnosis and treatment for non-functional pancreatic neuroendocrine neoplasms with diameter <2 cm

“…The "diameter criteria" for small pNENs is applicable and practicable in clinical practice for the following reasons and can also be applied to cystic pNENs. [6,7] Pathologically, small pNENs are usually low-grade, with pNET G1, pNET G2, and pNET G3/pNEC accounting for approximately 82%, [8][9][10] 16%, [8][9][10] and 1% to 2%, [8][9][10] respectively. In terms of staging, the rate of lymph node metastasis (11.0%-21.2%) [3,6,10,11] and distant metastasis (0%-7.6%) [3,5,10,12] are significantly lower than those with larger diameters.…”

“…[6,7] Pathologically, small pNENs are usually low-grade, with pNET G1, pNET G2, and pNET G3/pNEC accounting for approximately 82%, [8][9][10] 16%, [8][9][10] and 1% to 2%, [8][9][10] respectively. In terms of staging, the rate of lymph node metastasis (11.0%-21.2%) [3,6,10,11] and distant metastasis (0%-7.6%) [3,5,10,12] are significantly lower than those with larger diameters. [13,14] Regarding prognosis, the rate of postoperative recurrence and metastasis of small pNENs is also lower (about 2%-7%).…”