Malignant transformation of a vestibular schwannoma after gamma knife radiosurgery.
OBJECTIVE: To report a single case of malignant transformation of a vestibular schwannoma after radiosurgery and review the growing body of literature describing patients with malignant transformation of primary benign tumors after radiosurgery, including vestibular schwannoma.
METHODS: A 46-year-old woman presented with right facial paresthesias and imaging consistent with a right-sided vestibular schwannoma (volume approximately 18.5 cm(3)).
RESULTS: The patient underwent subtotal resection followed by Gamma Knife radiosurgery (GKRS) 6 months after surgery. Initial histology showed a benign vestibular schwannoma with an MIB-1 labeling index of 5.7%. At 43 months after GKRS, the patient underwent repeat subtotal resection of a benign vestibular schwannoma (MIB-1 labeling index 7.4%). At 59 months after GKRS, she underwent a third resection, and histology showed frank malignant transformation (MIB-1 labeling index 33.8%).
CONCLUSIONS: Malignant vestibular nerve tumors are extremely rare; only 18 cases have been reported in the literature. Our patient is the sixth pathologically confirmed case of malignant transformation after radiosurgery, supporting the contention that radiosurgery itself may play a causative role in transformation. In a histologically benign lesion, the presence of an elevated MIB-1 labeling index may predispose toward malignant transformation in the setting of adjuvant radiosurgery.
Medical Subject Headings
Brain Stem Neoplasms; Cell Transformation, Neoplastic; Craniotomy; Facial Paralysis; Fatal Outcome; Female; Humans; Ki-67 Antigen; Magnetic Resonance Imaging; Middle Aged; Neoplasm Recurrence, Local; Nervous System Diseases; Neuroma, Acoustic; Postoperative Complications; Radiosurgery
Digital Object Identifier (DOI)
Yanamadala, Vijay; Williamson, Richard W; Fusco, David J; Eschbacher, Jennifer M; Weisskopf, Peter; and Porter, Randall W, "Malignant transformation of a vestibular schwannoma after gamma knife radiosurgery." (2013). Neurosurgery Articles. 700.