12/9/2008 Case 2: Anaplastic olgo(astro) with rhabdoid features

Presented by: Dr. Rao - Downstate Medical Center

Clinical History:

A 47 year old woman presented with altered mental status.  Neuroradiological workup revealed abnormal T2 signal over a large area involving left fronto-temporal lobes and extending along the corpus callosum into the right frontal lobe.  Evidence of marked compression of the left lateral ventricle, midline left to right shift, and vasogenic edema were seen.  The lesion was heterogeneous and involved the frontal, parietal and temporal lobes.  The lesion was subtotally resected.

Histology showed a round cell tumor with large atypical cells and satellitosis.  Some areas showed an astrocytic appearance with small anaplastic cells.  Some cells had copious pink cytoplasm reminiscent of gemistocytes, or Rhabdoid cells.   There were many mitoses, some of which were atypical.  There was a perivascular pattern. 

Immunohistochemistry showed many cells to be GFAP-positive.  Some of the intracytoplasmic inclusions were positive for both GFAP and vimentin.  The tumor was negative with SMA, cd34, EMA, synaptophysin, NeuN, and neurofilaments.  KI67/MIB1 showed 10-20% of cells to be in the proliferative mode.  P53 was strongly positive. 

Diagnostic Notes:

The diagnosis was malignant mixed glioma (anaplastic oligoastrocytoma) with rhabdoid features.

Discussion centered on the diagnosis and classification of glial and glioneuronal tumors with rhabdoid cells.  This group may include astroblastoma, ATRT arising in PXA, ATRT arising in irradiated optic ganglioglioma, rhabdoid glioblastoma multiforme, and large cell medulloblastoma with focal rhabdoid features.  It was pointed out that we need to characterize tumor with Rhabdoid features as to which have and which do not have the INI1 mutation.  It was also noted that the INI1 mutation is not specific for ATRT and renal rhabdoid tumors.

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