New Concepts Of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) consist of a heterogeneous group of malignancies with various clinical presentations and growth rates. The incidence has been estimated to 1-2 per 100,000 people per year. The largest group is the gastroenteropancreatic NETs While Less common locations are bronchopulmonary, thymus, skin, and genitourinary tract. Neuroendocrine tumors can develop either sporadically or in association with familial syndromes such as multiple endocrine neoplasia type -1 (MEN-1), multiple endocrine neoplasia type-2 (MEN-2) or von Hippel–Lindau (VHL). A classification system (World Health Organization) was established in year 2000 and recently updated in 2010, taking into consideration the histopathology and tumor biology of the tumors. The diagnosis of a NET is based on histopathology on tumor specimens, circulating biomarkers as well as imaging. Factors that determine the outcome of patients with neuroendocrine tumors are complex and multifaceted. These include the site of origin, the size of the primary tumor, and the anatomical extent of disease. Immunohistochemical indicators of a poorer prognosis are the degree of expression of the proliferation protein Ki-67 and the p53 tumor suppressor protein. Adverse clinical indicators are carcinoid syndrome, carcinoid heart disease, and high concentrations of the tumor markers, urinary 5-HIAA and plasma chromogranin A.The five year survival is mainly associated with the stage being 93% in local disease, 74% in regional disease and 19% in metastatic disease. Novel agents targeting the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) have demonstrated promising activity in patients with advanced neuroendocrine tumor.