[Neurendocrine tumours of the appendix, colon and rectum: current surgical aspects]

Neuroendocrine tumours (NET) are a heterogeneous group of neoplasms deriving from a system of diffuse neuroendocrine cells in organs and tissues, defined as the "diffuse neuroendocrine system". Over the period from 1996 to 2005 42 patients with gastroenteropancreatic (GEP) NET were observed (M.F ratio: 1.5:1; mean age 58 years; > 60 years for all localisations except the appendix [< 39 years]). Twenty-three were tumours of the appendix, colon and rectum, corresponding to 55% of all those affecting the digestive tract: 8 appendix (35%), 6 right colon (26%), 4 left colon (17%) and 5 rectum (22%). The NET diagnosis was formulated in all cases on the basis of histological and immunohistochemical examinations. The mean follow-up period was 5 years (range: 1-10). In the RO-RI cases no relapses occurred and those who were not disease-free were treated with somatostatin analogues and/or chemotherapy. NET of the appendix, colon and rectum are rare, despite being the most frequent among the GEP tumours, and are difficult to diagnose, and therefore sometimes pose problems of surgical therapy, which, when performed in time, may be curative. NET of the appendix measuring <2 cm, localised in the distal part without local infiltration, can be treated by simple appendicectomy and removal of the mesenteriole; otherwise, right hemicolectomy is indicated. The surgical treatment of tumours of the colon, except for well differentiated cases measuring <2 cm with a pedunculate structure such as to allow safe endoscopic removal, consists in radical hemicolectomy with lymphadenectomy. Carcinoids of the rectum measuring <1 cm and 1 cm to 2 cm, in the absence of other negative prognostic factors, can be treated locally by transanal endoscopic microsurgery (TEM) or minimally invasive transanal surgery (MITAS). Tumours measuring >2 cm or presenting muscular invasion and/or lymph-node metastases (malignant carcinoids), regardless of tumour diameter, are submitted to radical operations, as in the case of carcinoma of the rectum. Extensive disease which is no longer curable with surgery alone is treated with chemotherapy and bio-chemotherapy, but it is above all treatment with somatostatin analogues that plays a major role in symptom control.