Neuroendocrine tumours

Neuroendocrine tumours (NETs) are a diverse group of rare tumours arising from neuroendocrine cells throughout the body and with a wide spectrum of tumour biology and clinical behaviour. Most are well-differentiated, slow-growing tumours, whilst a minority are aggressive. NETs are classified based on tumour grading (Ki-67 and mitotic index) and tumour location. NETs can arise anywhere in the body, but the majority (60%–70%) arise from the gastroenteropancreatic system (GEP-NET) and the lungs (30%) (1). Most NETs are non-functioning; however, up to 30% of NETs are functioning tumours with hypersecretion of various biogenic amines and peptide hormones predisposing patients to clinical syndromes with symptoms such as diarrhoea, flushing, hyperglycaemia, or hypoglycaemia.