Only a handful of cases of de-novo
malignancies of the vestibulocochlear nerve have been reported. Even rarer is the malignant transformation of a previously histologically diagnosed benign
vestibular schwannoma. We present the case of a young adult who had combined operative/Gamma knife treatment for a benign
vestibular schwannoma, followed by further surgery 2 years later. He represented 10 years after original diagnosis with facial
numbness and
ataxia, MRI showing gross
tumor recurrence. After radical resection, histology showed malignant transformation to a
malignant peripheral nerve sheath tumor. Within 3 months there was rapid, aggressive recurrence with brainstem compression, requiring further surgery for brainstem
decompression. Histology confirmed further de-differentiation to an anaplastic
sarcoma. While awaiting
radiotherapy the
tumor recurred again, the patient succumbing. The patient had no features of
neurofibromatosis type 2. In the literature there are 13 other cases of malignant vestibular schwannomata. Only six had
radiotherapy and of these only two had histological confirmation of a benign lesion preradiotherapy. Neither of these had
neurofibromatosis. Three other cases had histological proof of
malignancy postradiosurgery, but with no preradiotherapy histology; of these, two were positive for
neurofibromatosis. The
tumor biology of vestibular schwannomata as well as the radiobiology in the context of malignant transformation is discussed.