The prevalence and incidence of neuroendocrine tumors (NETs) are increasing in the pediatric population. This increase can be associated with improved diagnostics and increased detection rates of the disease. We aimed to discuss the clinical and pathological characteristics of patients with this rare disease who were followed and treated at our center.The medical records of children (aged 0-18 years) with NETs of the digestive system, followed up and treated between 2007 and 2020 at Ondokuz Mayis University Faculty of Medicine, were reviewed.Overall, 16 patients (8 girls and 8 boys) were analyzed. Fifteen patients had NETs in the appendix; 14 of these had grade I NETs, and 1 had grade II NETs. No additional surgery was performed except for appendectomy. All patients were in complete remission at the last follow-up (median 38 months). The other patient, a 12-year-old girl, had a primary hepatic neuroendocrine carcinoma (grade III NET). Three cycles of neoadjuvant and adjuvant platinum-based chemotherapy were administered, and right hepatectomy was performed to remove the mass. The patient is being followed-up for approximately 3 years without disease recurrence.Most NETs are observed in adults, and most studies have focused on this population. Unlike adults, increasing awareness of the disease in the pediatric population (especially in cases of acute appendicitis), discovering therapeutic treatments, and sharing experiences are crucial for developing an optimal therapeutic approach for pediatric NETs.

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a heterogeneous group of epithelial neoplasms originating from the diffuse neuroendocrine cell system of the gastrointestinal tract and pancreas. They are very rare, especially in pediatric age, and vary widely in terms of clinical presentation, malignant potential, and prognosis.

A 9 years' old, white female child presented with abdominal pain and diarrhea mixed with bright red blood lasting 2 days followed by hematemesis.

Routine laboratory tests revealed microcytic anemia. Upper endoscopy showed a 20-mm polypoid lesion in the posterior wall of the duodenal bulb. Biopsy specimens were taken and histologic analysis showed a well-differentiated neuroendocrine tumor G1, with a ki-67 index <2%, an expression of chromogranine A (CgA), synaptophysin and somatostatin receptor type 2A (SSTR2A). Endoscopic ultrasound showed a 21-mm hypoechoic, hypervascular lesion involving the mucosal, submucosal, and muscular layers and a 15-mm hypoechoic round periduodenal lymph node. Gallium-68-somatostatin receptor positron emission tomography (PET with Ga-DOTATOC) showed one area of tracer uptake in the duodenum and other one near the duodenum compatible with the primary tumor site and a lymph node respectively. All the tests confirmed the diagnosis of a GEP-NET of the duodenal bulb, with a single lymph-node metastasis.

The patient underwent an open duodenal wedge resection.

The follow-up at 6, 24, and 36 months and then yearly after surgery for a total of 42 months showed no evidence of recurrence.

Duodenal neuroendocrine tumors represent 1% to 3% of all GEP-NETs. They are rare in adults and extremely rare in children. Therefore, the diagnostic and therapeutic approach should be multidisciplinary, including laboratory, endoscopic, and specific imaging tests and strictly follows guidelines, to avoid misdiagnosis and inadequate treatments. Although the prognosis is benign in most cases, they can present with metastases. Therefore, a careful follow-up is extremely important.