Background: How malignant insulinomas present relative to benign insulinomas is unknown.
Methods: A single-institution retrospective study identified patients with insulinoma. Malignancy was defined by distant metastases, positive lymph node(s), T stage of 4, direct invasion into surrounding peripancreatic tissue, or presence of lymphovascular invasion. Wilcoxon Rank Sum tests and Kaplan-Meier analysis were used.
Results: A total of 311 patients were identified: 51 malignant and 260 benign. Patients with malignant insulinoma presented with higher levels of insulin, proinsulin, and c-peptide. Malignant lesions were larger: 4.2 ± 3.2 vs 1.8 ± 0.8 cm in benign lesions, p < 0.01. Overall survival at 5 years was 66.8% vs 95.4% for malignant and benign insulinoma respectively, p < 0.01.
Conclusions: Larger size of insulinoma and increased serum β-cell polypeptide concentrations were associated with malignancy. Malignant insulinoma has poorer survival. Further work-up to rule out malignancy may be indicated for larger pancreatic lesions and for patients with higher pre-operative insulin and pro-insulin.
Keywords: Insulinoma; Pancreas; Pancreatic neuroendocrine tumor.
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