Abstract
Neuroendocrine neoplasms (NEN) appear homogeneous in terms of morphology, but constitute
a very heterogeneous group of tumors in terms of biological and clinical features.
NEN may occur in any organ, but are most commonly observed in the lung and the gastroenteropancreatic
system (GEP). The European Neuroendocrine Tumor Society (ENETS) developed guidelines
in the last 5 years to standardize and improve the diagnosis and therapy of GEP-NEN.
Taking these guidelines into account, the TNM classification of the Union for International
Cancer Control (UICC) was introduced in 2009. The new GEP-NEN classification of the
World Health Organization (WHO) was presented 1 year later. According to the guidelines
of the ENETS, the UICC, and the WHO, the pathology classification of NEN of GEP consists
of several basic components: (1) evidence of the neuroendocrine nature of the tumor,
(2) histological distinction between well and poorly differentiated tumors, (3) proliferation-based
grading. (4) TNM staging (including data about vascular invasion and resection margins),
(5) with reference to the clinical question: evidence of hormones and biogenic amines,
and (6) optional, especially in cases of initial diagnosis of NEN: expression of the
somatostatin receptor type 2A. Based on these criteria, a standardized prognostic
stratification of GEP-NEN can be performed in combination with other clinical parameters.
The novel classifications constitute the basis for selecting the procedures of molecular
and metabolic imaging as well as for tumor-specific treatments and permit comparisons
of larger tumor populations. Close interdisciplinary cooperation is a prerequisite.
Key words
grading - hormones - molecular imaging - neuroendocrine tumor - TNM classification
