73IN - Classification and Tumor Biology of Nets

Abstract

ABSTRACT First recognized as “carcinoids” in the gastroenteropancreatic (GEP) tract, neuroendocrine tumors (NET) are a variety of neoplastic lesions distributed in most organs and apparata. The current World Health Organization (WHO 2010) define low and high grade neuroendocrine cancer types with the broad definition of neuroendocrine neoplasms and introduces grading (G1-G3) and Tumour Node Metastasis (TNM) staging for class definition. The proposed WHO 2010 grading system defines three classes (G1-G3) according to both mitotic count and Ki67 index. Three classes are defined as WHO class 1, neuroendocrine tumor (NET), G1; WHO class 2, NET G2 and WHO class 3, neuroendocrine carcinoma (NEC), by definition G3. The definition of NET equalizes the previous definition of carcinoid (typical and atypical as variably utilized in the pathology literature) and of well-differentiated endocrine tumor/carcinoma as from the previous WHO classification. The WHO 2010 TNM substantially endorsed the classification originally proposed by the European Neuroendocrine Tumour Society (ENETS) with two exceptions in that i) it limits its application to NET G1-G2 (carcinoids) and ii) it shows significant differences for pancreas and appendix TNM definitions. In general a common staging system frame was defined with stage I tumors with limited growth, stage II larger or more invasive tumors, in absence of metastases, stage III tumors invading the surrounding structures or with loco-regional metastases and stage IV implying distant metastases. This classification system was first adopted by the International Union Against Cancer (UICC) and subsequently endorsed by both the American joint Cancer Committee (AJCC) and the WHO. Current oncology guidelines for Neuroendocrine neoplasms are largely based on proliferation fraction and stage to define specific therapeutic options. Disclosure G. Rindi: In the last three years I acted as consultant for Ipsen pharma and received speaker's fee/honoraria from Novartis pharma, Ipsen pharma and Pfizer.