Case 1b -

Low Grade Oligodendroglioma Timothy Smith and Cynthia Welsh

The low grade oligodendroglioma has evenly placed small cells and small capillaries around nests of cells ("chicken wire fencing") on tissue sections. The "haloes or fried eggs" so promptly diagnostic on permanent sections, are an artifact of fixation, and won't be seen on frozen sections. On smears the cells will have only a small rim of cytoplasm, if any, without the long processes of an astrocyte (often the cytoplasm is stripped off leaving bare nuclei), so the DDX includes other small cell processes. The clinical history and radiologic findings sharply limit the real DDX. Nuclei having a large enough rim may be termed "mini- or micro- gemistocytes". The nuclei tend to be rounder, less irregular, and less pleomorphic than those of astrocytomas. Oligodendrogliomas commonly have calcifications, but these can be confused with corpora amylacea, bone dust or other debris. Microcysts are typical in many low grade tumors, including oligodendroglial. Satellitosis of tumor cells around neurons is so frequent, that the tumors seem on scans to be cortical based. Microcystic (NOTE - these are all tumors!) Meningioma Pilocytic astrocytoma Pilomyxoid astrocytoma Oligodendroglioma DNET Ganglion cell tumors Craniopharyngioma PNST Ependymoma Subependymoma Teratoma Astroblastoma Fibrillary astrocytoma - rarely Calcifications Normal in pineal, choroid plexus, and meninges Seen in non-neoplastic conditions, especially injury in children Tumors: Oligodendroglioma-common in cortex Neurocytoma-common SEGA-common Astroblastoma Astrocytoma-occasional Ganglion cell tumors Ependymoma (particularly clear cell subtype) Pilocytic-occasional