Mistaken identity: granular cell astrocytoma masquerading as histiocytosis of the central nervous system.

[erdheim-chester disease]

Granular cell astrocytoma (GCA ) is an uncommon malignant glial tumour that is associated with a poor prognosis . GCA cells have some morphological and immunohistochemical similarities to macrophages . In this case , a small biopsy contained no typical astrocytoma and large rounded lesional cells were interpreted as negative for glial fibrillary acidic protein and S 100 and positive for CD 68 , a commonly used marker for macrophages . A diagnosis of a histiocytosis was made . When the patient failed to respond to first and second line therapy , tumour resection was undertaken and the pathology then showed typical morphologic and immunohistochemical features of glioblastoma (astrocytoma World Health Organization grade IV ).