Presentation
Increasing thigh and buttock pain and straight leg raise test positive.
Patient Data
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There is a well defined intradural ovoid lesion that is centered within the distal lumbosacral canal. Lesion fills the canal space from the L5-S2 levels. The lesion is confined to the canal without extension into the adjacent exit foramen. The lesion measures 5.5 x 1.5 x 2.2 cm in vertical, AP and transverse dimensions respectively. It is difficult to determine if the mass arises from a specific nerve root. The lesion has heterogeneous signal characteristics. The lesion predominately low signal on T2 weighted images with areas of moderate signal within. The lesion is isointense to CSF on T1 weighted images and enhances fairly homogeneously post contrast. On STIR weighted imaging the lesion is predominantly moderate signal intensity with areas of low signal within which likely represent blood products.
Histology
MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of a moderately hypercellular tumor composed of cells with uniform round and oval nuclei with finely granular chromatin and delicate processes. These are arranged in diffuse sheets and perivascular pseudo-rosettes. No mitotic figures are seen and there is no vascular endothelial cell hyperplasia and no necrosis. Myxoid-mucinous material is noted in some of the pseudo-rosettes interposed between the central blood vessel and the surrounding corona of tumor cells. Tumor cells show strong immunostaining for GFAP. Weak staining for epithelial membrane antigen (EMA) is noted in some pseudo-rosettes. The features are of myxopapillary ependymoma. The Ki-67/MIB-1 labeling index is <1%. 4. The section shows a dense collagenous membrane covered on one surface by tumor with features as described in specimens 1-3. No nerve tissue is identified.
FINAL DIAGNOSIS: Myxopapillary ependymoma.(WHO Grade I)
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The intradural mass ( * ) demonstrates mixed low and high T2 signal, with signal loss (blue arrows) best seen on STIR imaging suggesting blood products. The mass demonstrates enhancement.
Case Discussion
This case illustrates slightly atypical, but still characteristic, appearances of a myxopapillary ependymoma with evidence of some intratumoral hemorrhage.
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