Recent Advances in Management of CARCINOID Tumor of the Gastrointestinal Tract

Abstract

SUMMARY C arcinoid tumors are rare, slow-growing neuroendocrine tumors arising from enterochromaffin cells primarily in the submucosa of the intestine, accounting for 2-5%of all malignancy and carcinoid tumour comprise the majority, 55%. It belongs to the apudomas (amine precursor uptake and decarboxylation tumours), as it arises from endocrine amine precursor uptake and decarboxylation cells that can be found throughout the GIT. It can occur in any organ derived from the primitive endoderm but 64% originates in the GIT, with the commonest primary sites being the appendix, small intestines and rectum. In the small intestine, majority of the cases are found in the ileum, less commonly in the jejunum and rarely involving the duodenum. The induction of cellular proliferation by paracrine agents and growth factors is believed to follow mutations in oncogenes and tumour suppressor genes and the amplification of HER-2/neu cellular oncogene expression has been detected in ileal carcinoids. It has been found that stimulation of a number of the 5HT receptor subtypes, of which there are 15, has the potential to induce malignant transformation. The tumor arises in the Kulchitsky cells in the crypts of Liberkuhn and grows as a submucosal nodule. It is usually small, slow growing, and often invades transmurally. Metastases occur in 30% of patients at the time of diagnosis even though the mucosa is usually intact. It spreads characteristically to the lymphatics and adjacent mesentery. The direct local effect is elastic sclerosis of the mesenteric vessels and due to the marked fibrotic reaction, it results in angulations and fixation of the adjacent bowel loops. The annual incidence is thought to be 1.5-2 cases per 100 000 of the general population Recent studies have reported an increase in incidence to 3.84-8.4 per100 000 population. The highest incidence is reported in patients around 50-70 years old with no gender predilection Appendiceal carcinoid is an exception as it seems to develop at an earlier age and more frequently in women, which is thought to parallel the mean age at appendectomy. It is asymptomatic in up to 60% of the patients and autopsy studies showed that up to two thirds of jejunoileal carcinoids remain. Undetected in life. When symptoms occur, they are often non-specific and vary according to the location of the lesion. The prognosis varies depending on multiple factors including location, histological subtype, residual disease post resection and metastasis. In addition, some authors have reported the levels of 5-HIAA, plasma chromagranin A, weight loss and tumour size to be important factors.