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.