In recent years, there has been growing interest in the human gut microbiota, whose health is characterised by high microbial diversity. Through the gut-brain axis, the microbiota influences the homeostasis of the central nervous system by regulating neurological, immune and epigenetic functions. Intestinal dysbiosis is associated with various neurological and oncological diseases, including paediatric diseases and colorectal cancer. Recent studies highlight a significant link between microbiota and brain tumours: cancer patients show reduced microbial richness and altered bacterial composition. In addition, an intratumoural microbial population has been identified that can influence tumour initiation, progression and response to therapies by modulating tumour cells and the immune system. The aim of this study is to analyse stool samples to study the microbiota in children suspected CNS brain tumor as there are currently no studies of this kind reported in the literature to assess whether microbial changes can be detected at diagnosis, can be found during the course of the disease or are associated with tumour progression.

Inclusion Criteria:

• aged between 3 and 18 years with suspected CNS tumour undergoing neurosurgery (intracranial and spinal localisation)
• Patients who have not undergone prolonged antibiotic or probiotic therapy in the three months prior to sample collection.
• Signature of informed consent form.

Exclusion Criteria:

• personal history of chronic inflammatory bowel disease (colitis, Crohn's disease, ulcerative colitis) and congenital or acquired gastrointestinal diseases (coeliac disease, diverticulitis and diverticulosis, peritonitis, Hirschsprung's disease, short bowel syndrome, intestinal malrotation or duplication, intestinal atresia, omphalocele, presence of stomas, acute gastroenteritis)
• history of previous cancer-related treatments
• diagnosis of brain tumour not confirmed by histology (data obtainable post-surgery)