Postoperative Radiotherapy for Intracranial Ependymoma: Analysis of Prognostic Factors and Patterns of Failure

The long-term results of external beam radiotherapy following surgical resection in patients with intracranial ependymomas were evaluated to identify the prognostic factors and the pattern of recurrence. Between June 1961 and January 1999, 48 patients with intracranial ependymoma were treated with external beam irradiation with <40Gy following surgery. Total doses of 40.5–63.4Gy were delivered to the tumor site in 22–46 fractions over 33–101 days. Six patients with spinal deposit or positive cerebrospinal fluid cytology received whole spinal axis irradiation, and 4 patients received prophylactic spinal irradiation. The median follow-up of surviving patients was 110 months. The 10-year overall and relapse-free survival rates were 47% and 42%, respectively. In multivariate analysis, female gender, lower tumor grade and total resection were found to be associated with better relapse-free survival. Twenty of 26 recurrences developed at the primary tumor site (inside the irradiation field), two at the unirradiated cerebellum and spinal cord, and four at the spinal cord without intracranial failure. Only one of 34 patients with supratentorial tumors developed isolated spinal metastasis, whereas 3 of 14 patients with infratentorial tumors did so. Regarding the late neurotoxicity of radiotherapy, one of the 15 long-term (<4 years) survivors whose psychosocial status could be evaluated showed marked cognitive impairment. It was suggested that the use of new treatment strategies to improve local control would be warranted, and that prophylactic whole spinal axis irradiation appeared to be of more benefit in patients with infratentorial tumors than in those with supratentorial tumors.     

Postoperative radiotherapy of primary spinal cord tumors

During the 30 year period from 1957 to 1986, 42 patients with primary tumors arising from the spinal cord or cauda equina received postoperative irradiation at the University of California, San Francisco. Twenty-one patients had ependymomas: 18 were localized to one site, and 3 diffusely involved the cord. There were 12 patients with low grade astrocytomas and 3 with highly anaplastic astrocytoma or glioblastoma multiforme. All astrocytomas were localized at presentation. In 6 cases tissue was insufficient to permit a histologic diagnosis. Thirty-nine patients (93%) received total radiation doses ranging between 45.0-54.7 Gy using standard fractionation. The 10-year actuarial disease-specific survival rate for patients with localized ependymoma was 93%; 33% of these tumors recurred locally. The corresponding rate for diffuse ependymomas was 50%; the spinal disease was controlled in all 3 patients, but one developed a cerebral metastasis despite prophylactic cranial irradiation. Low-grade astrocytoma patients had a 10-year actuarial disease-specific survival rate of 91%, with 33% of these tumors recurring locally. No patient with highly anaplastic astrocytoma or glioblastoma multiforme survived longer than 8 months; all of these tumors recurred locally, and two of the three also developed diffuse craniospinal axis metastases. Local recurrence for ependymoma was delayed as long as 12 years following treatment, while all but one astrocytoma failure occurred within 3 years of treatment. No significant dose-response relationship with respect to local control was noted for either localized ependymomas or low grade astrocytomas. One patient developed radiation myelitis after receiving 50.4 Gy with standard fractionation. These results indicate that patients who undergo postoperative irradiation for low grade spinal astrocytomas and localized spinal ependymomas achieve excellent survival. However, despite treatment with total radiation doses taken to the practical limit of spinal cord tolerance, local failure remains common.     

Intracranial ependymoma long term outcome,patterns of failure

We analyzed 31 patients with intracranial ependymoma, all verified by secondary neuropathology review. There were 12 patients with ependymomas and 19 patients with anaplastic ependymoma by the WHO classification. Eight patients received craniospinal irradiation, 22 patients received cranial irradiation alone, and one patient was treated with chemotherapy alone. The median follow-up time was 11 years. The 5- and 10-year progression-free survivals (PFS) were 60% and 48%. Those with anaplastic tumors had a decreased 10 year PFS over those with low grade lesions: 26% vs. 55% (p=0.02). Delivering spinal irradiation in addition to cranial irradiation did not improve outcome. There were relapses in 16 patients. All patients relapsed at the primary intracranial sites with no spinal failures. Patients treated with whole brain irradiation had decreased 10 year PFS over those treated with local fields: 19% vs. 64% (p=0.006). Those patients treated to 50 Gy had an improved long-term PFS (p=0.04). Multivariate analysis was undertaken with the following variables: extent of cranial irradiation, pathology, anatomic site of ependymoma, cranial irradiation dose, extent of surgery, and whether spinal irradiation was given. With PFS as the endpoint, only extent of cranial irradiation (favoring local fields) and pathology (favoring low grade ependymoma) were significant prognosticators. We conclude that carefully outlined local field irradiation is the therapy of choice, and elective spinal irradiation is of questionable benefit.     

Light microscopic demonstration of the microlumen of ependymoma: A study of the usefulness of antigen retrieval for epithelial membrane antigen (EMA) immunostaining

To determine the origin of dotlike epithelial membrane antigen (EMA) immunoreactivity of ependymoma, which is consistent with the eosinophilic globular body in hematoxylin and eosin (H&E) stain, an immuno-electron microscopic study was undertaken. The usefulness of antigen retrieval pretreatment in detecting the dotlike EMA immunoreactivity in ependymomas was also studied. The materials were 29 ependymomas, 7 autopsy brains as a normal control, and 50 brain tumors of various types. The study confirmed that most of the brown dots in EMA immunostain in ependymoma represented microlumina of tumor cells. In ependymomas, plain EMA immunostaining showed dotlike positivity in only six cases (21%), and antigen retrieval pretreatment increased the number of positives up to 26 cases (90%). Antigen retrieved CD99 detected 23 positive cases (80%) in ependymomas. On the basis of the results, although some false positive findings were raised by antigen retrieval pretreatment, the authors positively recommend adoption of the technique, especially when ependymoma remains as one of the differential diagnoses of the tumor.     

Histological spectrum of ependymomas and correlation of p53 and Ki-67 expression with ependymoma grade and subtype

BACKGROUND: Clinical and histological criteria for ependymoma prognosis are well recognized. Recently few studies have been done based on Immunohistochemistry for prognostication of these tumours. In this study we have correlated the histological spectrum with immmunoexpression of p53 and Ki67 in these tumors. AIMS: To know the incidence of ependymomas; study their morphological spectrum and to evaluate expression of P53 and Ki 67 in different morphological subtypes. MATERIAL AND METHOD: A retrospective study was preformed on 70 ependymomas received in a period between 1994 and 2001. Entire tissue received was processed for routine paraffin embedded H&E stained sections. Immunocytochemistry was performed using antibodies to GFAP, EMA, Pancytokeratin and synaptophysin, to differentiate papillary ependymoma from choroid plexus papilloma; clear cell ependymoma from oligodendroglioma and central neurocytoma; ependymoblastoma from other embryonal tumours. p53 and Ki-67 immunohistochemistry was performed to correlate their expression with various tumour grades and subtypes. RESULTS: There were 3 cases (4.2%) of Grade I ependymoma (2 cases of myxopapillary ependymoma and 1 case of subependymoma); 57 cases (81.5%) of ependymoma grade II (43 of these were of classical variety, 11 of clear cell ependymoma, 2 of papillary and 1 case of cellular ependymoma). There were 9 cases (12.8%) of anaplastic ependymoma (one of these was a clear cell ependymoma and 1 case (1.5%) of ependymoblastoma CONCLUSION: p53 and Ki67 indices can be used in routine diagnostic laboratories to supplement the tumor grade on histology and more studies with follow up should be performed to analyse the prognosis of different subtypes. The expression of Ki 67 and p53 was significantly higher in anaplastic ependymomas. 4 out of 11 cases of clear cell ependymomas showed higher Ki 67 indices as compared to classical grade II ependymomas, thus further highlighting the importance of differentiating the various subtypes.     

Long-term outcomes of surgical resection with or without adjuvant radiation therapy for treatment of spinal ependymoma: a retrospective multicenter study by the Korea Spinal Oncology Research Group

Background

We sought to determine the surgical treatment and functional outcome and identify the predictors of survival in a retrospective cohort of patients with spinal cord ependymoma using data collected from the Korea Spinal Oncology Research Group database.

Methods

The data regarding 88 patients who had been surgically treated for histologically confirmed spinal cord intramedullary and extramedullary ependymoma from January 1989 to December 2009 were retrospectively reviewed.

Results

Histopathological examination revealed myxopapillary ependymoma in 24 patients, ependymoma in 61 patients, and anaplastic ependymoma in 3 patients. Gross total removal was achieved in 72 patients, subtotal removal in 15 patients, and partial removal in 1 patient. Twenty patients were treated with postoperative radiation. Fifty-two patients had stable or improved postoperative neurological function, while 36 experienced neurological deterioration. A permanent decrease in McCormick classification grade was seen in 17 patients. The progression-free survival rate was 87% for all patients at 5 years and 80% at 10 years. During follow-up, local recurrence/progression was seen in 13 patients. Diffuse meningeal spread developed in 2 anaplastic ependymoma patients. Postoperative radiotherapy after incomplete resection did not significantly correlate with longer times to recurrence. Multivariate analysis revealed histology and surgical extent of resection as independent predictors of longer progression-free survival.

Conclusions

Gross total removal alone is a good treatment strategy for spinal ependymomas. Early diagnosis and surgery, before severe paralysis, are important to obtain good functional outcomes. Subtotal resection with radiation therapy for intramedullary lesions appears to offer no advantages over gross total removal.     

A case of cervicomedullary junction tanycytic ependymoma associated with marked cyst formation

Tanycytic ependymomas are a subtype of ependymomas that were formally recognized as a new pathological entity in the latest World Health Organization (WHO) classification of 2000. They occur mostly in the spinal cord. Only a few reports have analyzed the proliferative potentials of these tumors; however, it has been reported that the MIB-1 labeling index of tanycytic ependymoma is lower than that of other subtypes of WHO grade II ependymomas. We report a rare case of cervicomedullary junction tanycytic ependymoma associated with marked cyst formation. A 62-year-old man had a history of progressive gait disturbance, diplopia, and swallowing disturbance over a one-month period prior to admission. Magnetic resonance imaging (MRI) showed a cystic mass with a mural nodule at the cervicomedullary junction with Gd-DTPA enhancement. Cyst-subarachnoid shunt was performed using a far lateral approach. After 6 years, however, the man was readmitted to the hospital because of reaccumulation of the cyst. Partial removal of a mural nodule and a cyst-subarachnoid shunt were performed simultaneously by a midline suboccipital approach. The pathological diagnosis was tanycytic ependymoma. Postoperatively, the patient recovered well and was discharged from the hospital without further treatment. Most of the tumor cells had small, round nuclei; pleomorphism was minimal. The cytoplasm was dilated. The tumor cells were positive for EMA and s-100, and negative for CD-34. GFAP was not determined due to difficulty caused by background glial processes. The MIB-1 labeling index was less than 1%. Ultrastructurally, the tumor cells had ependymal cell features, such as desmosomes and microvilli. Based on these findings, the pathological diagnosis was tanycytic ependymoma.     

Adjuvant radiotherapy delays recurrence following subtotal resection of spinal cord ependymomas

Background

Ependymoma is the most common glial tumor of the adult spinal cord. Current consensus recommends surgical resection with gross total resection (GTR) whenever possible. We performed a comprehensive review of the literature to evaluate whether adjuvant radiotherapy after subtotal resection (STR) has any benefit.

Methods

A PubMed search was performed to identify adult patients with spinal cord ependymoma who underwent surgical resection. Only patients who had clearly defined extent of resection with or without adjuvant radiotherapy were included for analysis. Kaplan-Meier and multivariate Cox regression survival analyses were performed to determine the effects of adjuvant radiotherapy on progression-free survival (PFS) and overall survival (OS).

Results

A total of 348 patients underwent surgical resection of spinal cord ependymomas, where GTR was obtained in 77.0% (268/348) of patients. Among those who received STR, 58.8% (47/80) received adjuvant radiotherapy. PFS was significantly prolonged among those who received adjuvant radiotherapy after STR (log rank; P < .001). This prolonged PFS with adjuvant radiotherapy remained significant in multivariate Cox regression analysis (STR versus STR + RT group; hazard ratio (HR) = 2.26, P = .047). By contrast, improved OS was only associated with GTR (GTR versus STR + RT group; HR = 0.07, P = .001) and benign ependymomas (HR = 0.16, P = .001).

Conclusions

Surgery remains the mainstay treatment for spinal cord ependymomas, where GTR provides optimal outcomes with longest PFS and OS. Adjuvant radiotherapy prolongs PFS after STR significantly, and OS is improved by GTR and benign tumor grade only.     

Treatment of spinal cord ependymomas by surgery with or without postoperative radiotherapy

Purpose: To evaluate the effectiveness of complete resection and postoperative radiotherapy in spinal cord ependymomas. Methods and materials: We conducted a retrospective study over 20 patients (13 males and 7 females) with histologically confirmed spinal cord ependymomas between July 1985 and April 2001. Among them, 13 patients had ependymomas, 6 had myxopapillary ependymomas, and 1 had anaplastic ependymoma. All patients received radical surgery for tumor removal with 13 patients achieving complete resection and 7 incomplete resection due to technical difficulty. Among those with incomplete resection, 6 patients received postoperative radiotherapy to tumor bed and only one patient with anaplastic ependymoma received surgery alone. The total tumor dose ranged from 50 to 60 Gy. Results: Among the 20 patients, 19 patients were alive and showed local control. The median survival time of all patients was 109 months, with 104 months in the complete resection alone group and 135 months in the incomplete resection with postoperative radiotherapy group. One patient with anaplastic ependymoma and no postoperative radiotherapy developed leptomeningeal seeding 9 months after surgery. Salvage therapy of radiotherapy and chemotherapy maintained normal neurological functions. The patient expired 34 months from the initial diagnosis due to progression of leptomeningeal seeding. Conclusion: Complete resection alone in spinal cord ependymoma can achieve excellent local control and survival. Patients should receive complete resection if technically possible. Postoperative radiotherapy is not recommended for complete resection. For incomplete resection, postoperative local radiotherapy is recommended and it can also achieve excellent local control and survival. Local radiotherapy with 50-60 Gy is effective and safe. Salvage radiotherapy improves quality of life for local recurrence or leptomeningeal seeding patients.     

Surgical Outcome and Prognostic Factors of Spinal Intramedullary Ependymomas in Adults

The goal of treatment for spinal ependymoma is complete removal with minimal postoperative neurological deficit. The authors correlated the results of surgical management for spinal cord ependymoma with the rate of postoperative disease progression and the prognostic factors. Thirty-one cases of spinal ependymomas, surgically treated between 1979 and 1998, were retrospectively analyzed. The authors reviewed clinical features, radiological characteristics and operative findings for the surgical outcome analysis. Thirty-five percent of patients with preoperative Nuricks grade better than grade 4 showed improvement in functional status, whereas no improvement was observed in patients with preoperatively poorer functional status (P=0.05). The proportion of complete surgical removals was influenced by tumor location (40% in cases around the conus versus 97% in other regions, P=0.003) and histology (42% in the myxopapillary subtype versus 97% in the non-myxopapillary subtype, P=0.001). Disease progression was observed in six cases, the mean progression free interval after surgical removal was 83 months and the 5-year progression free rate was 70%. Disease progression was found in two out of 23 cases from the complete removal group and in four out of eight cases from the incomplete removal group (P=0.008). In the aspect of disease progression, the only statistically significant factor by multivariate analysis was the surgical extent of removal (P=0.010). Of those patients where there was incomplete removal, radiation therapy lead to improved clinical results, which were not statistically significant (P=0.27). In the surgical treatment of spinal cord ependymoma, preoperative functional status and the extent of removal were the significant prognostic factors influencing postoperative outcome. Early diagnosis is vital and complete removal of the tumor should be attempted in all surgical treatment of spinal ependymoma.     

CDKN2A/p16 in ependymomas

Sixteen cases of ependymoma were studied for CDKN2A/p16 inactivation by immunohistochemistry using a p16 monoclonal antibody, by homozygous deletion (HD) assay and 5CpG promoter methylation assay (methylation-specific PCR). Three out of 16 cases were p16 immuno-negative: two corresponded to grade II ependymomas and one to grade III. The latter ependymoma, characterized by a high Ki-67/MIB-1 LI, was the only one of the whole series to show CDKN2A HD. No promoter methylation was found in the two immuno-negative cases without CDKN2A HD. Alternative mechanisms, such as point mutations or alterations in p16 post-translational regulation, may be responsible for p16 inactivation. Since in our series just one out of eight anaplastic cases showed negative immunostaining and CDKN2A HD, p16/CDKN2A inactivation may not play an important role in the malignant transformation of ependymomas.Amplification of CCND1 and CDK4, p27/Kip1 degradation and TP53 mutations were previously studied by other authors and were demonstrated not to correlate with anaplasia. Up to date, molecular genetic studies have not been useful in recognizing the anaplastic variant in ependymomas.     

Diffusion differences between pilocytic astrocytomas and grade II ependymomas

Background

The aim of our study was to differentiate between cerebellar pilocytic astrocytomas and grade II ependymomas on the basis of their diffusion properties.

Patients and methods

The study prospectively included 12 patients with pilocytic astrocytomas and 5 with ependymomas. Apparent diffusion coefficients (ADC) were compared between tumour types.

Results

ADC values were significantly higher in pilocytic astrocytomas than ependymomas, with almost no overlapping of the range of measured ADCs between the two tumour types.

Conclusions

Significant diffusion differences between pilocytic astrocytomas and grade II ependymomas enable their preoperative distinction, in combination with conventional magnetic resonance images.     

Radiation tolerance of the spinal cord previously-damaged by tumor and operation: Long term neurological improvement and time-dose-volume relationships after irradiation of intraspinal gliomas

Of 26 patients with intramedullary spinal cord gliomas (9 astrocytomas, 5 glioblastomas, 12 ependymomas) seen at the Massachusetts General Hospital from 1962–1980, 24 were irradiated (21 initially and 3 after post-surgical recurrence). Those 19 patients who survived at least 1 year after completion of irradiation were evaluated for post-irradiation neurological changes. No patient developed radiation myelopathy. Return to a permanently and completely normal neurological status occurred for $\text{33}\text{51}$ (65%) of pre-irradiation neurological deficits. The major cause of post-irradiation neurological deterioration was tumor recurrence.Although 18/19 patients had their thoracic or lumbar spinal cords irradiated, each with field sizes greater than 10 cm, spinal cord doses approaching, equalling, or occasionally exceeding various definitions of spinal cord tolerance were tolerated well without evidence of radiation myelopathy. Spinal cords of patients with intramedullary gliomas, often with major neurological deficits prior to irradiation, may be treated safely to doses approaching or equalling spinal cord tolerance levels. These doses are expected to locally control most ependymomas and astrocytomas without an increased risk of radiation myelopathy. Caution should be observed if doses higher than this are contemplated in an attempt to cure a glioblastoma, because the 5 % tolerance level of the damaged spinal cord remains to be defined.     

Adult intradural primary spinal cord tumors

Primary spinal cord tumors represent 4.5% of all central nervous system neoplasms. They are either intradural intramedullary or intradural extramedullary. Intramedullary tumors are predominantly intrinsic gliomas (astrocytomas and ependymomas). Spinal ependymomas can usually be completely removed by separating the tumor from the spinal cord and, when complete, no further therapy is required. Astrocytomas, by contrast, infiltrate the myelon, and therefore surgery is frequently incomplete. Intradural extramedullary tumors are mostly benign (WHO grade 1) and comprise either peripheral nerve sheath tumors (neurofibromas and schwannomas) or meningiomas. Complete resection can be performed on both lesions and is often curative. Radiotherapy is indicated for primary malignant tumors (WHO grade 3 and higher) and for patients in whom surgery is contraindicated. For grade 1 and 2 tumors, the role of radiotherapy is controversial. Chemotherapy is reserved for recurrent primary spinal cord tumors with no other options. However, the lack of clinical trials for these tumors is problematic. Consequently, treatment is similar to that for intracranial histologies. Early recognition of the signs and symptoms of primary spinal cord tumors facilitates early treatment, potentially minimizes neurologic morbidity, and improves outcome. Primary treatment for almost all spinal cord tumors is surgery, with predictors of outcome being preoperative functional status, grade of tumor, and extent of resection.     

Intracranial ependymomas: results of treatment with partial or whole brain irradiation without spinal irradiation

Twenty patients with intracranial ependymoma (16) or anaplastic ependymoma (4) received post-operative radiation therapy at the University of California, San Francisco from 1959 through 1981. No patient received prophylactic spinal irradiation. The actuarial survival at 5, 10, and 15 years for 15 patients with ependymoma who received greater than 45 Gy was 67, 57, and 46%, respectively. Only one patient (7%) developed clinically recognized spinal metastases; this patient was eventually shown to have tumor at the primary site, within the irradiated volume. Six of 11 patients treated with partial brain irradiation had an intracranial recurrence, versus 1 of 4 patients treated with whole brain irradiation. Three patients were autopsied after failing partial brain irradiation for an ependymoma and the site of failure was within the irradiated volume of each patient. Partial brain irradiation was used to treat 4 patients with anaplastic ependymoma. One developed a local recurrence within the irradiated volume. The other three survived longer than 10 years. At UCSF, most patients with low grade ependymomas are presently treated with partial brain irradiation, but whole brain plus spinal irradiation is used for anaplastic tumors.     

Pediatric Intramedullary Spinal Cord Tumors: Special Considerations

Intramedullary spinal cord tumors (IMSCTs) of the pediatric population are rare and comprise thirty-five percent of intraspinal neoplasms. Low-grade astrocytomas predominate; ependymomas increase in frequency with ascending age and become the most frequent IMSCT in adults. Gangliogliomas are very rare in adults but comprise nearly thirty percent of tumors in children under three years of age. The cervical spine is the region of the spine most affected. Pain is the most common presenting symptom with weakness, gait deterioration, torticollis also frequently reported. Hydrocephalus occurs with greater frequency than in adult patients and often requires a shunt. Motor and sensory evoked potential monitoring is routinely utilized. Osteoplastic laminotomy is performed to forestall the development of progressive spinal deformity. Gross total resection is feasible in most ependymomas and results in surgical cure. Astrocytomas are infiltrating neoplasms and gross total resection is occasionally possible only in the pediatric population. However, the role of radical resection of low-grade fibrillary astrocytomas of the spinal cord in children has not been definitively demonstrated in the literature. Outcome for low-grade astrocytomas is better in children than adults, but not as favorable as that for ependymomas. Malignant tumors have dismal outcomes and surgery in these patients serves only to provide a diagnosis.     

Ependymoma: Results,Prognostic Factors and Treatment Recommendations

Purpose: To review the University of Florida experience in treating ependymomas, analyze prognostic factors, and provide treatment recommendations.Methods and Materials: Forty-one patients with ependymoma and no metastases outside the central nervous system received postoperative radiotherapy with curative intent between 1966 and 1989. Ten patients had supratentorial lesions, 22 had infratentorial lesions, and 9 had spinal cord lesions. All patients had surgery (stereotactic biopsy, subtotal resection, or gross total resection). Most patients with high-grade lesions received radiotherapy to the craniospinal axis. Low-grade intracranial lesions received more limited treatment. Spinal cord lesions were treated using either partial spine or whole spine fields.Results: Of 32 intracranial tumors, 21 recurred, all at the primary site; no spinal cord tumors recurred. Overall 10-year survival rates were 51% (absolute) and 46% (relapse-free); by tumor site: spinal cord, 100%; infratentorial, 45%; supratentorial, 20% (p = 0.002). On multivariate analysis, tumor site was the only factor that influenced absolute survival (p = 0.0004); other factors evaluated included grade, gender, age, duration of symptoms, resection extent, primary tumor dose, treatment field extent, surgery-to–radiotherapy interval, and days under radiotherapy treatment.Conclusions: Patients with supratentorial or infratentorial tumors receive irradiation, regardless of grade. Craniospinal-axis fields are used when spinal seeding is radiographically or pathologically evident. Spinal cord tumors are treated using localized fields to the primary site if not completely resected. Failure to control disease at the primary site remains the main impediment to cure.     

Radiation Therapy and the Management of Intramedullary Spinal Cord Tumors

The use of radiation therapy in the management of intramedullary spinal cord tumors remains controversial. Several studies indicate that the use of postoperative radiation therapy modestly improves both local control and survival in spinal cord ependymomas and astrocytomas. Modern treatment planning and imaging allow more accurate target definition and respect for related normal tissue tolerances.     

Epithelial differentiation in intraspinal meningiomas

To investigate the epithelial features of intraspinal meningiomas, 25 intraspinal meningiomas and 25 intracranial meningiomas were examined for the presence of pseudopsammoma bodies with hematoxylin-eosin and periodic acid-Schiff staining. In addition, we investigated the expression of keratin and epithelial membrane antigen (EMA) by immunohistochemical methods. Pseudopsammoma bodies were found in 3 of 25 cases of intracranial meningiomas (12%), but no definitive pseudopsammoma bodies were observed the intraspinal mengiomas. Three cases (12%) of intraspinal meningiomas and 9 cases (36%) of intracranial meningiomas, including 3 cases with pseudopsammoma bodies, were immunoreactive for keratin. All 25 (100%) intracranial meningiomas and 20 of 25 (84%) intraspinal meningiomas were reactive for EMA. In the intraspinal meningiomas, 4 of 25 cases (16%) showed no reactivity for EMA. These findings suggest that the origin of certain cell components of meningiomas may be different according to the site of the tumor or that the nature of meningioma may be modified by the local environment.     

Improved localization of infratentorial ependymoma by magnetic resonance imaging: Implications for radiation treatment planning

Ependymomas of the posterior fossa extend into the upper cervical spinal cord in approximately one-third of cases. Unfortunately, the posterior fossa and upper cervical cord region is often poorly seen on computed tomography (CT), making radiotherapy planning difficult. We report five cases of posterior fossa ependymoma with extension into the cervical cord where magnetic resonance imaging (MRI) demonstrated the caudal extent of tumor more clearly than CT. The extent of tumor depicted by MRI in each case correlated well with the operative findings. Higher doses of radiotherapy to the entire tumor volume are associated with improved survival in infratentorial ependymoma; however, the radiation tolerance of the cervical spinal cord is close to the dose necessary to control posterior fossa ependymoma, making limitation of radiation field volumes important. MRI may provide a method of precisely defining caudal tumor extent of posterior fossa ependymomas so that limited volume, high dose radiotherapy can be more safely administered to these patients.