Vestibular schwannoma with malignant transformation: a case report.

We describe a rare case of malignant transformation in a vestibular schwannoma in a 33-yr-old woman. She presented herself with headache, tinnitus, and hearing loss and underwent posterior fossa explorations three times during the short period of 3 months. The clinicopathological features of the original tumor were typical of benign vestibular schwannoma. Despite a complete microsurgical excision, two months later, the tumor recurred locally with a rapid increase in size causing a progressive worsening of neurological symptoms. A diagnosis of malignant schwannoma was made for the recurrent tumor on the basis of the microscopic findings of high cellularity, moderate pleomorphism, and the presence of mitotic cells. Repeat magnetic resonance imaging performed a month after the second surgery unexpectedly showed definite tumor enlargement. She remained clinically stable following the third debulking of the tumor and adjuvant radiotherapy. We propose that this recurrent tumor represent malignant transformation from a benign vestibular schwannoma which was an unusual occurrence in a patient without neurofibromatosis.