The term ‘karzinoide’was originally used by receptorsubtypes, whicharemembersofseven5HT receptor groups distinguished according to their Obendorfer in 1907 to describe a carcinoma-like lesion without malignant qualities. These tumours coupling to particular signalling pathways and amino acid sequence identity. 2 Apart from the 5HT3 recepare uncommon, and attract the interest of clinicians because of the spectacular symptoms that they cause. tor, which is a ligand-gated ion channel, they are all G-protein-coupled receptors. Stimulation of a These symptoms are so striking as to make clinical diagnosis obvious, but because of their range, unfor- number of the 5HT receptor subtypes has the potential to induce malignant transformation. Activation tunately result in patients being cared for by many different medical and surgical specialists. Carcinoid of rat 5-HT2c receptors induces malignant transformation of transfected N1H-323 cells. 3 Activation tumours, even when there is metastatic spread, are generally thought to have a good prognosis and as of mouse 5HT2b receptors expressed in L+ kD cells activates p21ras and p42mapk/p44mapk and leads to the a result, patients with this condition are managed symptomatically. development of 5HT2b-dependent 5HT-stimulated foci in confluent cells which are tumourigenic in However, Godwin et al. assessed survival in 2837 patients with carcinoids, and in patients with liver nude mice. 4 metastases and raised urinary 5HIAA levels he reported a five-year survival of 18–38% and a median survival of 23 months. 1 These figures suggest The treatment of metastatic carcinoid that carcinoid tumour is a rather more aggressive tumours disease than is generally appreciated. In this article we review recent clinical developments, make a