Prognostic impact of a large mesenteric mass >2 cm in ileal neuroendocrine tumors

BACKGROUND AND OBJECTIVES: Ileal neuroendocrine tumors (i-NETs) frequently metastasize to mesenteric lymph nodes and the liver. Regional lymphadenopathy is associated with desmoplasia of the mesentery forming a large mesenteric mass (LMM). Although the latest American Joint Committee on Cancer TNM staging (8th edition) defined LMM >2 cm as N2, the prognostic impact of LMM is ill-defined. We evaluated whether LMM is prognostic for patients with i-NETs. METHODS: This single-institution, retrospective cohort study included 106 patients who underwent resection of i-NETs between 2007 and 2018. Overall survival (OS) and liver progression-free survival (LPFS) were compared between patients with and without LMM. RESULTS: LMM was present in 66 patients (62%) and was not associated with the presence or absence of liver metastasis (P = .969) or the extent of liver involvement (P = .938). OS and LPFS differed significantly between patients with and without LMM (5-year OS rates of 64.8% and 92.9%, respectively, P = .011; 3-year LPFS rates of 45.3% and 67.5%, respectively, P = .025). In multivariate analysis, LMM was an independent prognostic factor for both OS (hazard ratio: 4.69, 95% confidence interval: 1.63-17.6) and LPFS (1.99, 1.08-3.88). CONCLUSION: LMM >2 cm is prognostic for OS and LPFS and represents aggressive tumor biology.