Symptomatic subependymoma: a clinicopathological and flow cytometric study

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✓ Twenty-one intracranial subependymomas were reviewed with regard to presentation, diagnosis, operative findings, and long-term follow-up data. The histopathological features were critically reviewed, and deoxyribunucleic acid analysis was performed by flow cytometry. The patients' mean age was 48.5 years (range 32 to 72 years). In 14 cases the tumor was located in the fourth ventricle, in six within a lateral ventricle, and in one in the third ventricle with extension into the lateral ventricle. Radiographic characteristics included isodensity with minimal enhancement on computerized tomography, frequent dystrophic calcification, and isointensity on T1-weighted or slight hyperintensity on T2-weighted magnetic resonance images. The predominant histological features in all cases were those of classic subependymoma. Nonetheless, pathological examination showed a minor (< 20%) ependymoma component in five cases, significant cytological atypia in seven, mitoses in 11, endothelial prominence in four, and focal hemorrhage-associated necrosis in two. Flow cytometry revealed a diploid pattern in 12 patients, tetraploidy in two, and aneuploidy in one.

Two patients died in the perioperative period. Of the remaining 19, 12 underwent gross total resection (two of whom received postoperative irradiation) and seven underwent subtotal resection (five of whom received irradiation). None of the 12 non-irradiated patients developed tumor progression or died of direct tumor-related causes. Of the seven irradiated patients, follow-up imaging studies demonstrated their tumors to be radioresponsive, particularly with doses of 5000 cGy or greater. Despite the presence of cytological atypia and mitotic activity in the majority of cases, the prognostic effects of such factors as tumor location and the extent of surgical resection outweighed those of the standard histopathological parameters. Routine postoperative irradiation is not recommended, but should be reserved for cases with a symptomatic residual or recurrent subependymomas following surgery.

Article Information

Address reprint requests to: Bernd W. Scheithauer, M.D., Surgical Pathology, Mayo Clinic, 200 First Street S.W., Rochester, Minnesota 55905.

© AANS, except where prohibited by US copyright law.

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Figures

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    Radiographic studies in a case of fourth-ventricular subependymoma. Left: Computerized tomography scan showing a well-demarcated lobulated fourth ventricular mass with moderate contrast enhancement and slight dystrophic calcification. Center and Right: On magnetic resonance imaging, the tumor appears isointense with central low intensity on the T1-weighted images (center) and hyperintense on the spin-density image (right).

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    Magnetic resonance images of a supratentorial subependymoma Left: A well-demarcated isointense septum pellucidum mass is seen on the T1-weighted image. Note an area of minimal dystrophic calcification. Right: On the spin-density image, the lesion appears as a hyperintense area.

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    Photomicrograph of a subependymoma specimen demonstrating the typical lobular growth pattern with central cellularity and peripheral skeins of fibrillated cell processes. H & E, × 43.

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    Photomicrographs of a subependymoma specimen. Left: Monotonous cells, typically clustered and devoid of atypia. Cytological uniformity characterizes the majority of subependymomas. H & E, × 180. Right: Section showing microcysts, a not uncommon finding. This appearance may be prominent in some examples. H & E, × 70.

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    Photomicrographs of subependymoma specimens. Although cytological uniformity characterizes subependymomas, fibrillary (left) and gemistocytic (center) astrocytes are not uncommon. The same is true of foci of cellular atypia (right). H & E. × 180.

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