Parameningeal embryonal rhabdomyosarcoma with leptomeningeal metastasis in a young adult female: illustrative case.

backgroundRhabdomyosarcoma (RMS) is a rare malignancy of undifferentiated skeletal muscle tissue and is the most common pediatric soft tissue sarcoma. Adolescent and young adult (AYA) patients (15-21 years of age) experience poorer outcomes compared with younger patients, primarily due to unfavorable histological subtypes, primary location, and tumor size. Tumors that arise from the skull base called parameningeal RMS have a poor prognosis due to anatomical complexity and the risk of leptomeningeal metastasis. OBSERVATIONS: The authors present the case of an 18-year-old female patient with a 4-month history of multiple progressive cranial neuropathies. MRI demonstrated a large left-sided mass centered at the foramen ovale with significant intracranial and infratemporal extension. Following near-total resection, pathology revealed embryonal RMS with anaplastic features. She subsequently began six cycles of high-dose vincristine, actinomycin, and cyclophosphamide therapy and proton radiation therapy. Two weeks after completing radiation therapy, follow-up imaging revealed a recurrence with leptomeningeal metastasis. Despite treatment with vincristine, irinotecan, and temozolomide chemotherapy, and craniospinal irradiation, the patient died of disease 5 months after spinal metastasis diagnosis. LESSONS: Genomic profiling might be considered for early integration as a standard practice in this population in cases of such aggressive and rare malignancies. https://thejns.org/doi/10.3171/CASE24755.