1984 Volume 36 Issue 4 Pages 813-823
An autopsy case of pontine astrocytoma with extensive subarachnoid dissemination was presented. The patient was a girl of 12 years old, who was admitted to the hospital because of decreased visual acuity and double vision. CT examination of the brain showed the findings consistent with neoplastic enlargement of the pons. Irradiation and immunotherapy afforded partial remission and she discharged 2 months after admission. Her symptoms, however, recurred 3 months after discharge and CT examination revealed obstructive hydrocephalus. Construction of ventriculo-peritoneal shunt afforded temporary reduction of her symptoms, but decerebrated posture appeared and her general condition progressively deteriorated. The patient died 1 year and 6 months after the onset of her initial symptoms.
Autopsy revealed diffuse neoplastic enlargement of th e pons and extensive dissemination of tumor tissue in the subarachnoid space over the cerebral ventral surface and cerebellopontine angles. Superficial cortical tissue adjacent to subarachnoid dissemination was found to be invaded secondarily by tumor tissue.
Histologically tumor in the pons showed the feature of well differentiated fibrillary astrocytoma with abundant production of glial fibrils. Cellular atypism was not prominent and mitotic figures were rare, but flowcytometric analysis of DNA distribution of this tumor showed an increase of tetraploid cells, suggesting malignancy.
Disseminated foci in subarachnoid spa ce showed highly cellular neoplasm composed of smallsized cells, which was reminiscent of medulloblastoma. Mitotic figures were abundant. Transitional features to fibrillary astrocytoma were apparent and intercellular deposition of acid mucopolysaccharides was seen in some areas. Reactive proliferation of vascular endothelial cells was prominent in subarachnoid tumor tissue. Deposition of tumor cells on the ependymal surface and secondary invasion into deep brain tissue was also noted.
Reports of astrocytoma in the brain stem with subarachnoid dissemination are rare. Rarer are the cases similar to ours in which disseminated foci in subarachnoid space were composed mainly of small anaplastic cells, while primary site in the brain stem showed the features of well differentiated fibrillary astrocytoma. Similar cases were reported by Friede et al. (1982) and designated by them as “infantile small cell glioma”. Our case and their cases suggest that small cells in astrocytomas represent highly malignant characteristics and are liable to spread diffusely in the subarachnoid space.
The significance of intercellu lar deposition of acid mucopolysaccharides in astrocytomas was also discussed. It was suggested that localized anoxia due to inappropriate vascular supply caused an increase of permeability of the vascular wall which resulted in the deposition of acid mucopolysaccharides in intercellular space.
