The objective of the International Rare Brain Tumor Registry (IRBTR) is to better understand rare brain tumors through the collection of biospecimens and matched clinical data of children, adolescents, and young adult patients diagnosed with rare brain tumors.

The International Rare Brain Tumor Registry (IRBTR) is a prospective observational study that will collect tumor samples and matched clinical and radiological data to better understand the outcomes of patients with rare brain tumors in particular: CNS sarcoma, BCOR, MN-1 altered tumors, PLAG/L1, and other rare or unclassified rare brain tumors.

Data collected include demographics, disease characteristics, treatment information, radiological imaging, and biospecimen collection if available ( tumor tissues Patients will be followed longitudinally to obtain outcome data. Data collection will continue for approximately 10 years.

Inclusion Criteria:

• Patients with a known or suspected CNS Sarcoma.
• Patients with a known or suspected BCOR-altered brain tumor
• Patients with a known or suspected Astroblastoma/NM-1 altered brain tumor
• Patients with known or suspected histologically ambiguous/unclassifiable brain tumor
• Patients with a known or suspected rare brain tumor.
• Signed informed consent by patient/ parent or guardian (assent where applicable) to participate in the study.

Exclusion Criteria:

• The patient has an extra-CNS primary tumor.
• The patient is older than 46 years of age at diagnosis.
• The patient or family is not willing to participate or does not sign informed consent.

The study population will include patients who have completed the informed consent process and are <= to 45 years of age at diagnosis of the following: CNS Sarcoma, BCOR-altered tumor, Astroblastoma/MNI-1 altered tumors, histologically ambiguous/unclassifiable brain tumor, rare brain tumor. Patients from anywhere in the world are eligible for enrollment.

IPD will not be shared with other researchers.