Neuroendocrine tumors of the small intestine causing a desmoplastic reaction of the mesentery are a more aggressive cohort.

BACKGROUND: Desmoplastic reaction of the mesentery is commonly seen in patients with neuroendocrine tumors of the small intestine. However, it is not clear whether desmoplastic reaction is associated with tumor-specific characteristics and diminished prognosis. Therefore, the aim of this study was to investigate whether the presence of a desmoplastic reaction correlates with prognostic and molecular markers of neuroendocrine tumors of the small intestine. METHODS: Patients with neuroendocrine tumors of the small intestine operated at our department from 2000 to 2016 were analyzed. Patient and tumor characteristics were evaluated. Kaplan-Meier and multivariate analyses were performed. RESULTS: In total, 148 patients underwent surgery, and preoperative imaging was available in 113 patients. A total of 45 patients showed desmoplastic reaction of the mesentery and progression-free survival was significantly impaired (26 months versus 65.4 months) compared with patients without desmoplastic reaction. These patients had significantly more often distant metastases (84.4% vs 39.7%), lymphatic vessel (68.9% vs 44.1%), and perineural tissue infiltration (57.8% vs 17.6%) compared with patients without desmoplastic reaction. However, proliferation index (positive desmoplastic reaction 4.1% versus negative desmoplastic reaction 3.3%) and tumor size (positive desmoplastic reaction 2 cm versus negative desmoplastic reaction 1.9 cm) were not diverging significantly. CONCLUSION: This study revealed that tumors leading to desmoplastic reaction are more aggressive, despite similar Ki67 indices.