Endocrine Abstracts

Neuroendocrine tumors encompass a heterogeneous group of tumors arising from the diffuse neuroendocrine system. The incidence of NETs rises with age, with the peak after 65 years. However, all NETs observed in adults may be diagnosed in children too. There are a very few studies addressing NETs in young patients. This study summarizes clinical, histopatological and genetic characteristics of young patients with NETs. This is a retrospective study describing clinical, histopathological and genetic characteristics in patients below 31 years of age, with NETs of various localizations, treated in one center from 2004–2018. Among 914 consecutive patients with NETs of different primary sites, 65(7.1%) patients 30 years of age or younger (age range 9 – 30, mean 23.5 years) were diagnosed (female 58.5%, male 41.5%). The number of diagnosed patients increased with age (age groups 0–10 years: 1, 11–20: 16, 21–30: 48 patients). The majority of them had pancreatic (pNETs, 30.8%), followed by appendiceal (24.6%) and bronchial NETs (brNETs, 23.1%). There was no difference in frequency of pNETs and brNETs in comparison to older patients (P> 0.05). Conversely, appendiceal NETs were significantly more frequent in young (24.6% vs. 2.6%, P<0.01) and were associated with appendicitis (14, 93.3%). The most frequent pNETs were NET-G2 (50%), followed by NET-G1 (23.3%) and NET-G3 tumors (20%). There was no difference in Ki-67 index between young and older patients with pNETs (P>0.05). However, metastatic disease at the time of diagnosis was more frequent in older patients (65.6% vs. 35.3%, P<0.01). The most frequent brNET was atypical carcinoid (46.7%), followed by typical carcinoid (40%) and small cell NEC (SCNEC, 13.3%). Ki-67 was significantly lower in younger patients (9.8% vs. 29.1%, P<0.01), although metastatic disease was equally present in both younger and older patients (P>0.05). Among all, metastatic disease was noted in 56.9% patients. Genetic cause was found in 12.3% patients having either pancreatic or brNETs. MEN1 gene mutations were found in 6 patients, one patient with pNET had VHL syndrome, one NF1. Except two patients with brNETs, all patients had associated tumors and positive family history. All MEN1 negative patients with multiple (n=2) or associated tumors (n=2) were screened for CDKN1b mutations, and were negative. The prevalence of different type of NETs in young patients is comparable with older patients, except for the appendiceal NETs. Metastatic disease is equally present as in older patients. Despite early tumorigenesis, genetic cause is known in a small portion of patients.