DISEASE CHARACTERISTICS: Histologically confirmed supratentorial anaplastic glioma with a recurrent cyst requiring aspiration for symptom control Measurable cystic lesion confirmed by contrast-enhanced CT or MRI At least 3 months since radiotherapy to site of measurable disease unless unequivocal evidence of tumor progression Neoplastic cell reactivity with tenascin demonstrated by immunohistology with either a polyclonal rabbit antibody or a monoclonal murine antibody