The assessment of malignancy in endocrine tumours of the gastrointestinal tract

Abstract

The recently released WHO classification of endocrine tumours provides a useful framework for assessment of malignancy of gastrointestinal endocrine neoplasms. This classification, based on a uniform scheme irrespective of the gastrointestinal region of tumour origin, comprises three main categories: (1) well-differentiated endocrine tumours that are further subdivided into those with benign and those with uncertain behaviour; (2) well-differentiated endocrine carcinomas (low grade); and (3) poorly differentiated endocrine carcinomas (high grade). Differentiation of tumours of group 1 vs groups 2 and 3 is based on common criteria universally applied in tumour diagnosis and has important implications for tumour prognosis and treatment. The differential criteria for assigning the tumours to subgroups 1.1 with benign evolution or 1.2 with uncertain (either benign or low-grade malignant) behaviour vary among the different regions of the digestive system and include the tumour size, the occurrence of angioinvasion, and, for some sites, the degree of cell proliferation and the presence of an associated endocrine syndrome. Further useful contribution to the assessment of tumour malignancy will be provided in the future by genetic studies that have already disclosed associations between specific gene defects and tumour malignancy.