Validation of WHO 2017 Classification and Identification of Prognostic Factors in Patients with Pancreatic Neuroendocrine Neoplasms: A Real-World Experience in Taiwan

<b>Background:</b> Pancreatic neuroendocrine tumors (PanNETs) are rare neoplasms with an increasing incidence. This study aims to validate the clinical relevance of the WHO 2017 classification system in the Taiwanese population and identify independent prognostic factors for patients with PanNETs. <b>Materials and methods:</b> We conducted a retrospective analysis of 176 patients with PanNETs from the Chang Gung Medical Hospital at Linkou in Taiwan, spanning the years 2009 to 2022. Pathology reports were reassessed according to the WHO 2017 classification. Clinical characteristics, treatment patterns, and survival outcomes were documented, with subgroup analyses to compare grade 3 (G3) neuroendocrine tumors and neuroendocrine carcinomas (NEC). <b>Results:</b> The overall 5-year survival rate was 58.7%, with median survival of 107.6 months. Survival rates showed clear stratification across WHO 2017 classifications: G1 (83.1%, median 141.0 months), G2 (55.0%, median 105.2 months), G3 (14.6%, median 21.5 months), and NEC (9.4%, median 19.6 months). Multivariate analysis identified five independent prognostic factors: age over 60 years (HR 1.70), tumor size >2cm (HR 1.893), lymph node involvement (HR 1.801), distant metastasis (HR 3.042), and NEC classification (HR 2.382). NEC demonstrated significantly higher lymph node involvement (81% vs 48%, p=0.026), higher Ki-67 index (69 vs 43.8, p<0.001), and higher rates of metastases compared with G3 NET. <b>Conclusions:</b> Our findings validate the prognostic utility of the WHO 2017 classification, particularly in differentiating NET G3 from NEC. This refined classification system, combined with identified prognostic factors, provides valuable guidance for clinical decision-making and treatment selection in patients with PanNETs.