Onkológia 5/2021
WHO classification of neuroendocrine neoplasms of the gastrointestinal tract and pancreas
Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumours showing different spectrum of morphological, immunohistochemical, molecular-genetic and clinical manifestations with different prognosis. This type of tumour can originate in virtually any organ of the human body with the most common occurrence in the gastrointestinal tract (GIT) and pancreas. Based on the knowledge of genetic changes of these tumours, a new system of classification and terminology of NENs was published in 2019 by World Health Organization (WHO), which represents a uniform framework of classification of these tumours across the spectrum of their possible occurrence in the body, which can significantly reduce confusion between pathologists and clinicians. This system divides NENs into three groups of tumours; a) well-differentiated neuroendocrine tumours (NETs) with possible histologic differentiation in the range of grade G1, G2 and G3 based on the evaluation of mitotic and proliferative activity (Ki-67 index); b) poorly differentiated neuroendocrine carcinomas (NECs), which are morphologically defined as small cell or large cell NEC and c) mixed neuroendocrine-non-neuroendocrine neoplasms (so-called MiNENs). Despite the uniform terminology, the current WHO classification 2019 also takes into account specific morphological features, clinical presentations, prognosis and genetic changes of NETs, NECs and MiNENs in individual organs of the GIT and pancreas, which are described in details in the relevant organ´s respective chapters. The result of the this uniform framework classification of NENs is standardization of approach to diagnosis and grading of NENs, even with the preservation of all additional information reflecting the unique features of each neuroendocrine tumour in individual localities of the human body.
Keywords: neuroendocrine neoplasm, neuroendocrine tumour, neuroendocrine carcinoma, WHO classification, grading
