Most islet cell tumours are benign lesions, while islet cell carcinoma is a highly malignant tumour. However, according to the current definition, islet cell tumours are classified as pancreatic neuroendocrine tumours and all neuroendocrine tumours have malignant potential, i.e. all have a tendency to recur or metastasise. Pathological grading would be helpful and is currently classified as G1, G2 and G3, with high-grade (G3) tumours having a more malignant tendency. Even islet cell tumours with a pathological tendency to be benign need to be followed up after radical surgery.