The ENETS and AJCC/UICC TNM classifications of the neuroendocrine tumors of the gastrointestinal tract and the pancreas: a statement

Abstract

In 2006 a working group of the European Neuroendocrine Tumor Society (ENETS) developed and published a proposal for a TNM staging classification of the neuroendocrine tumors (NET) of the foregut (stomach, duodenum, and pancreas), accompanied by a grading system [1]. This was followed in 2007 by the publication of a TNM staging classification of the midgut and hindgut NETs (ileum, appendix, colon/rectum) from the same group [2]. These were the first TNM classifications to be developed for the NETs that took into account the distinctive growth patterns of these tumors and that differentiated these tumors from the other gastroenteropancreatic (GEP) carcinomas. These classification systems additionally supplemented the WHO classification of the GEP-NETs [3], some aspects of which had already been recognized as prognostically relevant [4]. In the years that followed the publication of these proposed TNM classifications, the classifications that concerned the foregut GEP-NETs and particularly the pancreatic NETs were validated by several studies, and their biological relevance and power to discriminate among prognostic groups was largely confirmed [5–9]. In 2009 the seventh edition of the AJCC/UICC TNM classification of the most important malignant tumors appeared [10]. It also includes new TNM staging classifications of the gastrointestinal carcinoids and of pancreatic neuroendocrine tumors, which had not previously been included in the AJCC/UICC staging classifications. However, the seventh edition of the AJCC/UICC TNM classification does not apply to high grade (large cell and small cell) neuroendocrine carcinomas and does not exactly follow the ENETS classifications for some of the anatomic sites. No data are presented to justify the use of different staging parameters. The result is that there now exist two parallel systems, each of which uses identical TNM terminology but may refer to different types and extents of disease for certain NETs. This discrepancy will lead to much confusion among clinicians and will likely limit the ability to compare research G. Kloppel Consultation Center for Pancreatic and Endocrine Tumors, Department of Pathology, Technical University of Munich, Munich, Germany