An astrocytoma that arises from the brain stem and occurs during childhood. The disease is childhood brainstem astrocytoma (MONDO_0003870, a Monarch Disease Ontology id). Also known as: brain stem astrocytic neoplasm of childhood, childhood brain stem astrocytic neoplasm, childhood brain stem astrocytoma, paediatric brain stem astrocytic neoplasm, pediatric brain stem astrocytic neoplasm.