Neuroendocrine tumours (carcinoids) of the appendix

Neuroendocrine tumours (NETs) of the appendix (formerly ‘carcinoids’) are rare and are usually detected incidentally after appendectomy. Histopathologically they derive from a subepithelial cell population, which is different from NETs in other sites. They are preferentially located at the tip of the appendix. Tumours <1 cm hardly ever metastasize and are treated by appendectomy. Tumours >2 cm require right hemicolectomy because of a significant risk of metastatic spread. Treatment for lesions 1–2 cm is controversial and needs further characterization of the tumour (i.e. mesoappendiceal invasion, vascular invasion, mitotic activity, proliferation markers) and careful patient risk evaluation. Goblet-cell carcinoids have features resembling both carcinoid and adenocarcinoma and should be treated by hemicolectomy. Overall prognosis of small appendiceal NET is excellent in all ages.