CyberKnife radiation therapy for malignant myopericytoma in a pediatric patient: a case report and review of the literature.

Background: Malignant myopericytoma is a very rare malignant soft tissue tumor which usually develops during adulthood. It has a very poor prognosis due to its aggressive nature and frequent distant metastases.

Methods: In our case report, we present a 17-month-old girl with malignant myopericytoma who was successfully treated using CyberKnife (Accuray; Sunnyvale, CA, USA) stereotactic radiotherapy.

Results: A rare localization of the tumor caused significant challenges during the course of treatment. Radical surgical resection was not achievable due to the tumor's location in the inner ear; therefore chemotherapy was initially given to the patient. However, due to the fast progression of the tumor during chemotherapy, we decided to use CyberKnife stereotactic radiosurgery (SRS; 5 fractions of 7 Gy) in order to prevent further invasion of the surrounding tissues. During SRS, tumor growth stopped and the tumor then gradually regressed. Since completion of treatment (currently almost 5 years) our patient has been in complete remission without any significant side effects of the radiation therapy.

Conclusion: In our recent experience, systemic chemotherapy combined with CyberKnife SRS proved to be effective in a patient with a rare malignant myopericytoma.