Meningiomas are the most common primary brain tumors in adults but much less frequent in children. Many subtypes exist, including anaplastic (malignant) meningioma, which accounts for less than 20% of pediatric tumors. Meningiomas can arise in association with cancer predisposition syndromes due to germline variants in genes such as NF2, MEN1 and SMARCE1. This report describes a 6-year-old boy diagnosed with anaplastic meningioma who was treated with surgery and focal radiation therapy. The family consented to participate in the Texas KidsCanSeq clinical genomics study. Analysis of germline and tumor samples detected a single germline finding of a CDKN1B pathogenic frameshift variant associated with Multiple Endocrine Neoplasia Type 4 (MEN4) without somatic loss of the other allele. Tumor analysis revealed a YAP1::MAML2 fusion, which has been previously reported in pediatric meningiomas not associated with NF2. YAP1::MAML2 fusion is a known driver for development of meningioma, but the role of the germline CDKN1B variant in the absence of a tumor second hit is unclear. This case highlights the importance of performing combined tumor and germline molecular genetic analysis of rare tumors to help clarify the risk of development of cancer in patients with rare cancer predisposition syndromes.