Giant cell ependymoma of the filum terminale. A report of two cases

A case of myxopapillary ependymoma with predominant giant cell morphology: A rare entity with comprehensive genomic profiling and review of literature

In the evolving landscape of ependymoma classification, which integrates histological, molecular, and anatomical context, we detail a rare case divergent from the usual histopathological spectrum. We present the case of a 37-year-old man with symptomatic spinal cord compression at the L3-L4 level. Neuroradiological evaluation revealed an intradural, encapsulated mass. Histologically, the tumor displayed atypical features: bizarre pleomorphic giant cells, intranuclear inclusions, mitotic activity, and a profusion of eosinophilic cytoplasm with hyalinized vessels, deviating from the characteristic perivascular pseudorosettes or myxopapillary patterns. Immunohistochemical staining bolstered this divergence, marking the tumor cells positive for glial fibrillary acidic protein and epithelial membrane antigen with a characteristic ring-like pattern, and CD99 but negative for Olig-2. These markers, alongside methylation profiling, facilitated its classification as a myxopapillary ependymoma (MPE), despite the atypical histologic features. This profile underscores the necessity of a multifaceted diagnostic process, especially when histological presentation is uncommon, confirming the critical role of immunohistochemistry and molecular diagnostics in classifying morphologically ambiguous ependymomas and exemplifying the histological diversity within MPEs.

Giant-Cell Ependymoma of the Cervical Spinal Cord With Syringomyelia and Pathological Presentation: A Case Report and Review of the Literature

Ependymomas are unusual neuroepithelial tumors of the central nervous system that arise from clusters of ependymal cells. In adults, ependymomas are the most common primary spinal cord tumors. Nevertheless, only a few cases of large-cell ependymoma have been documented; these cases often involve the brain. Here, we report the case of a 43-year-old man who had a cervical spinal cord ependymoma with syringomyelia. The giant-cell ependymoma (GCE) in the spinal cord discussed in this case emphasizes the characteristics of GCE and the discrepancy between the pathological appearance, the surgical results, and the clinically good prognosis.

Extra-axial sacral soft tissue giant cell ependymoma affecting a child: Case report and review of the literature

An otherwise healthy eight-year-old girl presented with a mass in the soft tissue of the sacral region. The lesion was diagnosed as a vascular malformation on imaging studies, for which percutaneous sclerotherapy was attempted. The mass continued to grow and a complete resection was performed after four years. The pathological diagnosis was giant cell ependymoma (GCE). GCE is a term used to describe a rare histologic variant of ependymoma characterized by malignancy-like morphologic phenotype and indolent behavior. To the best of our knowledge, this is the first case of extra-axial soft tissue sacral GCE reported in a child.

Giant Cell-rich Tanycytic Ependymoma as Intramedullary Spinal Mass

Intramedullary spinal cord tumors are rare neoplasms and harbour full spectrum of primary neoplasms as seen within the intracranial compartment. They include tumors with diverse pathologies, arising in both adults and children and pose considerable diagnostic challenge. The differentials at this site include wide ranging pathologies from benign, circumscribed pilocytic to diffuse astrocytoma, myxopapillary or tanycytic ependymoma and malignant diffuse midline glioma. Rare instances of glioneuronal tumors, pleomorphic xanthoastrocytoma have also been described at this location. H3K27M mutant diffuse midline high grade glioma is the new entry to this list in 2016 updated WHO classification. We describe the morphologic features of a diagnostically challenging intramedullary spinal cord tumor masquerading as a high grade lesion due its cellular composition and discuss its differentials. The report also emphasizes the role of already established and recently introduced immunohistochemical markers and other ancillary techniques as useful adjuncts in the diagnosis.

Outcome predictors in the management of intramedullary classic ependymoma: An integrative survival analysis

This is a retrospective study.The aim of this study was to illustrate the survival outcomes of patients with classic ependymoma (CE) and identify potential prognostic factors.CE is the most common category of spinal ependymomas, but few published studies have discussed predictors of the survival outcome.A Boolean search of the PubMed, Embase, and OVID databases was conducted by 2 investigators independently. The objects were intramedullary grade II ependymoma according to 2007 WHO classification. Univariate Kaplan-Meier analysis and Log-Rank tests were performed to identify variables associated with progression-free survival (PFS) or overall survival (OS). Multivariate Cox regression was performed to assess hazard ratios (HRs) with 95% confidence intervals (95% CIs). Statistical analysis was performed by SPSS version 23.0 (IBM Corp.) with statistical significance defined as P < .05.A total of 35 studies were identified, including 169 cases of CE. The mean follow-up time across cases was 64.2 ± 51.5 months. Univariate analysis showed that patients who had undergone total resection (TR) had better PFS and OS than those with subtotal resection (STR) and biopsy (P = .002, P = .004, respectively). Within either univariate or multivariate analysis (P = .000, P = .07, respectively), histological type was an independent prognostic factor for PFS of CE [papillary type: HR 0.002, 95% CI (0.000-0.073), P = .001, tanycytic type: HR 0.010, 95% CI (0.000-0.218), P = .003].It was the first integrative analysis of CE to elucidate the correlation between kinds of factors and prognostic outcomes. Definite histological type and safely TR were foundation of CE's management.

LEVEL OF EVIDENCE

4.

Giant Cell Ependymoma of Cervicomedullary Junction: A Case Report of a Long-Term Survivor and Literature Review

BACKGROUND

Ependymoma accounts for 3%-9% of all neuroepithelial tumors. Giant cell ependymoma (GCE) is a rare and distinct variant, with only 22 cases described in the literature. The 2007 World Health Organization classification first acknowledged this rare subtype. The cytologic features of GCE include the presence of pleomorphic giant cells with several cellular atypias, which at intraoperative frozen diagnosis may appear to be high-grade glial lesions. Despite its apparently malignant histology, GCE seems to be a neoplasm with a relatively good prognosis. Extended tumor removal is the gold standard without adjuvant treatment.

CASE DESCRIPTION

We describe the first case, to our knowledge, of GCE situated at the cervicomedullary junction in a 62-year-old patient. Surgery was performed with combined intraoperative monitoring of motor evoked potentials and somatosensory evoked potentials. Intraoperative frozen diagnosis revealed a high-grade glial neoplasm; however, gross total resection was achieved. The definitive diagnosis was GCE. At follow-up evaluation 11 years after surgery, the patient did not present with any tumor recurrence.

CONCLUSIONS

As the intraoperative diagnosis can be misleading, whenever a cleavage plane is recognized, it is essential to perform a gross total resection with the aid of intraoperative neurophysiologic monitoring, to improve prognosis and neurologic outcome. Data reported in the literature show that prognosis is mainly influenced by grade of resection.

Intraoperative squash cytology and histology of giant cell ependymoma: A diagnostic dilemma

Giant cell ependymomas (GCE) are extremely rare tumors, with 24 cases described in the literature. Squash cytology is a rapid, reliable, simple technique for intraoperative consultation in neurosurgical practice. We describe a rare case of GCE arising at level of L4-L5 in a 66-year-old woman and discuss the cytologic/histologic features. Intraoperative smears were highly cellular with a prominent fibrillary background and exhibited papillary structures and sheets composed of highly atypical and bizarre cells. Some of the cells showed nuclear pseudoinclusions and rarely formed pseudorosette-like arrays. Intraoperative diagnosis was high grade glial tumor. On paraffin sections, besides extensive polymorphism, there were no microvascular proliferation, necrosis, and mitosis and the final diagnosis was WHO grade II GCE. GCE may be a diagnostic challenge on intraoperative smears, frozen, and paraffin sections. It must be kept in mind in the differential diagnosis of giant cell exhibiting benign and malignant tumors of brain.

Immunohistochemical features of giant cell ependymoma of the filum terminale with unusual clinical and radiological presentation

BACKGROUND

Giant cell ependymoma of the filum terminale is a rare variant, generally manifested as a well-circunscribed intradural mass with an indolent biological behavior.

CASE PRESENTATION

We describe the case of a 48-year-old Mexican female who non-relevant past medical history, that developed a GCE of the filum terminale. Magnetic resonance imaging and computed tomography revealed the presence of an intra-axial tumor extending from L3 to L5 with extra-medullary invasion. Therefore the tumor was considered unresectable and only incisional biopsy was obtained, establishing the tentative diagnosis of a poorly differentiated neoplasia. A second evaluation of the case revealed the presence of numerous non-cohesive pleomorphic giant cells with intranuclear inclusions and broad eosinophilic cytoplasm, alternating with intermediate size cells with round, hyperchromatic nuclei and forming a perivascular pseudo-rosettes pattern. The ependymal phenotype was supported by light microscopy and corroborated by immunohistochemistry analysis. The patient was subsequently treated with radiotherapy 54Gy. She is alive after a 27-month follow-up, with residual disease, difficulty ambulating and pain.

CONCLUSIONS

GCE of filum terminale may have an atypical clinical and radiological presentation, albeit with invasive characteristics and anaplasia on histologic analysis. However, its biological behavior is indolent and associated to longer survival. Due to the presence of giant cells, the differential diagnosis of other primary neoplasias at that site were considered, including paraganglioma, malignant peripheral nerve sheath tumors as well as metastatic malignant melanoma, adrenal carcinoma, thyroid gland carcinoma and urothelial carcinoma, that may all harbor giant cells.

Cellular pleomorphism in papillary tumors of the pineal region

Papillary tumor of the pineal region (PTPR) is a recently recognized entity. We present the pathologic findings of two cases of PTPR as examples, and discuss the presence of cellular pleomorphism in these tumors. Patient 1 is a 48-year-old man with a pineal region mass. The tumor had unique biphasic patterns, papillary/pseudopapillary areas, and increased mitotic activity. Juxtaposed areas had marked pleomorphism, including nuclear enlargement, smudgy chromatin, nuclear pseudoinclusions, and cytoplasmic vacuolation. Mitoses were absent in these areas. Immunohistochemical staining revealed strong S100 expression. CAM 5.2 and CK18 were strongly positive in a patchy fashion. MIB1 labeling indices were high in classic PTPR regions but very low in pleomorphic areas. Patient 2 was a 35-year-old male with a pineal region tumor characterized by papillary architecture and overall cellular monotony, rare mitoses, and pleomorphism as a more isolated finding, with associated nuclear enlargement and crowding. S100 and CAM 5.2 labeling were present, and MIB1 labeling index was very low throughout the tumor. We discuss the pathologic and phenotypic features of PTPR. Variable pleomorphism may be present, reflected in size variation and nuclear hyperchromasia, but was not accompanied by increased proliferative activity in these cases, suggesting a degenerative phenomenon.

Cytologic features of giant cell ependymoma: a case report and review of the literature

Here, we present a case of anaplastic giant cell ependymoma (GCE) occurring in a 15-year-old woman. Squash smear slides for intraoperative frozen section diagnosis revealed oval to round cell clusters with a papillary structure in a fibrillary background. This was occasionally accompanied by the presence of bizarre pleomorphic giant cells with hyperchromatic nuclei and prominent intranuclear inclusions. These intranuclear inclusions were a key clue to diagnosis of ependymoma. Histologic analysis revealed features of a high-grade tumor with perivascular pseudorosettes and bizarre pleomorphic giant cells, which established the diagnosis of GCE. We performed a review of literatures about the cytologic features of GCE, including our case, thus proposing that intraoperative frozen diagnosis of GCE would be established by squash smear preparations featuring the mitosis and necrosis, as well as the high cellularity, and the presence of giant cells showing hyperchromatic nuclei with eosinophilic cytoplasm and intranuclear inclusions/pseudoinclusions.

Giant cell ependymoma of the thoracic spinal cord

We report a new case of giant cell ependymoma (GCE) of the thoracic spinal cord. Ependymomas predominate in children and young adults and are frequently intracranial and infra-tentorial. However, a second age peak at 30-40 years is reported for spinal tumours. Microscopically, ependymomas show a large variety of histological features, among which a rare variant with giant cells. This 59-year-old woman presented with a 6-month history of numbness and burning sensation affecting the left lower limb and hemi-trunk. A cervico-thoracic MRI revealed a solid intra-medullary tumour at the level of T1-T3, slightly T1-hypointense, T2-hyperintense and contrast enhancing. A complete surgical resection was carried out through a C7 to T4 laminectomy. Recovery was complete with no sign of recurrence at 18-month follow-up. The initial histological diagnosis of glioblastoma was challenged on the basis of the imaging and operative findings of a well-circumscribed tumour. The case was sent to us for second opinion and we diagnosed a GCE, WHO grade II, with a biphasic pattern including a predominant giant cell component (>90%), with genetic evidence of polyploidy, and a very limited classic component, showing a characteristic loss of chromosome 22. Our report adds to the clinical, imaging, pathological and genetic characterisation of GCE and brings the first genetic evidence that these rare tumours are at least bi-clonal. It also suggests that GCE have a good prognosis after complete surgical resection.

Rare histological variants in ependymomas: histopathological analysis of 13 cases

Ependymomas are rare brain tumors representing about 3% of all intra-cerebral and spinal neoplasms. The WHO classification recognizes various rare histological ependymoma variants (i.e., lipidized ependymoma, giant cell ependymoma, etc.). However, a detailed analysis of a larger series of such cases is still lacking. We analyzed 13 case of ependymoma presenting unusual histological features. The data analysis of our series and its comparison to the cases published in literature did not reveal any close association between these features and the clinical parameters (such as age or localization). Moreover, some of these features can be found combined in individual tumors, suggesting that these variants may represent a spectrum of differentiation rather than true specific entities. However, awareness on these rare histological patterns in ependymomas is necessary in the differential diagnosis with other primary or secondary brain tumors.

Multiple chromosomal monosomies are characteristic of giant cell ependymoma

Giant cell ependymoma, a rare ependymoma subtype, was recently recognized as a separate diagnostic entity with variations both in malignant potential and course of disease. We analyzed the first supratentorial giant cell ependymoma using G-band karyotyping, DNA ploidy analysis, and array comparative genomic hybridization. The tumor was hypodiploid, and the karyotype showed multiple monosomies. This novel cytogenetic pattern seems specific for giant cell ependymoma as the only previous cytogenetic analysis of a giant cell ependymoma found similar monosomies. We were also able to analyze cytogenetically the subsequent recurrent tumor, phenotypically an anaplastic ependymoma, allowing a first insight into the genetic events involved in disease progression.

Ependymal tumors

Ependymomas represent a heterogeneous group of glial tumors whose biological behavior depends on various histological, molecular, and clinical variables. The scope of this chapter is to review the clinical and histo-logical features as well as the molecular genetics of ependymomas with special emphasis on their influence on tumor recurrence and prognosis. Furthermore, potential molecular targets for therapy are outlined.

Giant cell ependymoma of the thoracic spine: pathology case report

INTRODUCTION AND IMPORTANCE: Spinal ependymomas are slow-growing lesions that comprise the majority of primary spinal cord neoplasms. When surgery is indicated, the extent of tumor removal is most prognostic for long-term survival. Unusual histological subtypes can make intraoperative diagnosis spurious, possibly altering the surgical approach from gross total resection for ependymomas to debulking for high-grade astrocytomas.

CLINICAL PRESENTATION

We describe a 67-year-old woman with a thoracic spine intramedullary giant cell ependymoma. She presented with decreased lower extremity sensation leading to unsteadiness and an eventual fall. A physical examination revealed lower extremity hyperreflexia and ankle clonus, but no clear sensory level. Magnetic resonance imaging demonstrated an intramedullary T1 and T2 hypointense, homogenously enhancing lesion at T8 with extensive cephalad and caudal edema.

INTERVENTION AND TECHNIQUE

A laminectomy at T8 to T9 afforded gross total resection of the lesion that had a clear cleavage plane with normal spinal cord. Intraoperative pathology suggested a high-grade glioblastoma, but final section showed sporadic giant cells with marked pleomorphism, uniform immunofluorescence staining with both glial fibrillary acidic protein and cluster of differentiation 99, and high MIB-1 index. Electron microscopy showed "zipper-like" junctions. There were no detected genomic abnormalities consistent with glioblastoma.

CONCLUSION

We present this first reported case of thoracic spine giant cell ependymoma alongside scant literature yielding 1 case in the cervical spine and 2 cases at the filum terminale. Those cases had benign courses, whereas ours demonstrates a high degree of proliferation, making the malignant potential difficult to assess.

Giant cell ependymoma of the cervical spinal cord: case report and review of the literature

Ependymomas account for 2-6% of all central nervous system neoplasms. They develop from the ependymal cells that line the ventricular cavities of the brain and the central canal of the spinal cord, as well as from ependymal clusters in the filum terminale. Giant cell ependymoma (GCE) is a rare subtype, with few cases reported, mostly in the brain. We describe the case of a cervical spinal cord ependymoma with pleomorphic giant cells and focal calcifications occurring in a 25-year-old woman. Magnetic resonance imaging revealed a large multicystic and partially enhancing intramedullary tumour extending from C2 to C5. Intraoperative analysis of frozen section tissue fragments suggested a malignant tumour; however, an obvious cleavage plane was present around most of the mass, and a macroscopically complete tumour removal could be achieved. Subsequently, paraffin sections and immunohistochemical investigations revealed unequivocal evidence of a GCE with focal calcifications. This case, the second giant-cell ependymoma to be described in the spinal cord and the first with focal calcifications, highlights the features of GCE and the discrepancy between the worrisome histological appearance, the surgical findings and the clinical relatively good prognosis.

Suprasellar giant cell ependymoma: a rare neoplasm in a unique location

Ependymomas are glial tumors that usually present in the posterior fossa in children and in the spinal cord in adults. Giant cell ependymoma, a rare ependymal subtype only recently recognized as a diagnostic entity in the last decade, demonstrates pleomorphic giant cells admixed with features of typical ependymoma. Although only 8 giant cell ependymomas have been reported to date, none have been reported in the suprasellar space. Moreover, as these neoplasms demonstrate a high incidence of anaplastic grade, recognition of this ependymal subtype is paramount. We describe the presentation and pertinent radiologic, histologic, immunologic, and ultrastructural findings in conjunction with relevant clinical implications of the first reported case of a suprasellar giant cell ependymoma occurring in a 34-year-old female 7 years after an initial diagnosis of a medullary ependymoma with rare atypical giant cells, a potential tumor seeding culprit.

Giant cell ependymoma: a case report

Ependymomas account for 3-9% of all neuroepithelial tumors. A peculiar variant of ependymoma known as "giant cell ependymoma" ("GCE") is especially rarely reported, it may pose some difficulties for the diagnosing neuropathologist. Here we present a case of a giant cell ependymoma occuring in a 17-year-old patient with the history of 2-year recurrent headaches and a 1-month history of vision impairment. CT scanning demonstrated a mass in the left occipital lobe, arising from the occipital horn of the lateral ventricle. Histological, immunohistochemical and electron microscopic findings were consistent with high-grade ependymoma. Especially striking was the presence of bizzare pleomorphic giant cells which predominated in the tumor tissue. As a result the diagnosis of GCE was established. This type of neoplasm necessitates, at least in theory, differentiation with anaplastic oligodendroglioma, clear cell ependymoma, pleomorphic xanthoastrocytoma, giant cell glioblastoma, and subependymal giant cell astrocytoma. To date giant cell ependymomas (GCEs) were reported in seven cases in the literature. To the best of our knowledge this is the 8th case in the literature. In spite of apparently "worrisome" histology GCE seems to be a neoplasm with a relatively good prognosis.

Rare giant cell ependymoma in an octogenarian. Case report and review of the literature

Ependymomas are glial tumors that occur most often in children. In adults, ependymomas most often appear in the spinal cord. The World Health Organization recognizes several rare ependymoma subtypes, including the giant cell ependymoma of the terminal filum. The authors describe an unusual case of a posterior fossa giant cell ependymoma in an 89-year-old man presenting with vertigo and disequilibrium. Only seven cases of this tumor have been reported in the literature to date. The authors discuss the clinical presentation, radiological findings, pathological considerations, and surgical intervention in this patient and review the relevant literature.

Concomitant Conus Medullaris Ependymoma and Filum Terminale Lipoma: Case Report

OBJECTIVE:

Ependymomas of the conus medullaris-cauda equina-filum terminale region are typically solitary lesions. In this report, we describe the clinical presentation, radiographic findings, operative details, and pathological features of a patient with a conus medullaris ependymoma and a filum terminale lipoma.

CLINICAL PRESENTATION:

A 40-year-old woman presented with increasing low back pain and bowel and bladder dysfunction. Magnetic resonance imaging revealed a partially cystic enhancing lesion at the conus medullaris and a T1-weighted hyperintense mass within the filum terminale.

INTERVENTION:

An L2-L3 laminotomy/laminoplasty was performed for gross total resection of the mass. Histopathological examination demonstrated a conus medullaris ependymoma and filum terminale lipoma. The patient experienced complete resolution of her preoperative symptoms.

CONCLUSION:

Spinal cord ependymomas are almost exclusively single lesions and their coexistence with other pathological entities is rare. In this report, we describe a patient with a concomitant conus medullaris ependymoma and filum terminale lipoma.

Woman aged 24 years with fourth ventricular mass

April 2005. A woman aged 24 years presented with symptoms related to a tumor in the fourth ventricle. Cytologically, the tumor was biphasic with areas typical of a classic ependymoma, including rosettes, and other areas containing grossly atypical giant cells. Many tumor cells were GFAP-positive and ultrastructural examination revealed microvilli and cilia. The histopathologic abnormalities place this tumor among the ependymomas. Its focal giant cell phenotype is very rare, but has been reported in 4 intracranial or filum ependymomas.

Infratentorial giant cell ependymoma: a rare variant of ependymoma

We describe a giant cell ependymoma occurring in a 50-year-old man. The mass was located in the posterior aspect of the foramen magnum, extending from the cerebellar tonsil to the upper cervical spine. The tumor was a highly cellular neoplasm showing biphasic histology. Diffuse sheets of non-cohesive atypical giant cells, having eccentrically located single or multiple nuclei and plump eosinophilic cytoplasm, partly infiltrated the desmoplastic inflammatory stroma. Parts of perivascular pseudorosette-forming or pseudopapillary areas were composed of atypically elongated cells, which looked like conventional anaplastic ependymoma. There was a transitional area between two patterns. Numerous mitoses and focal necrosis were observed. Immunohistochemically, the tumor cells were immunoreactive for glial fibrillary acidic protein, vimentin, S-100 protein, and CD99. None of the tumor cells showed immunoreactivity for epithelial membrane antigen except for the intracytoplasmic lumen of a few vacuolated cells. Ultrastructurally, tumor cells were ependymal in nature; we noted cytoplasmic intermediate filaments and intercellular microrosettes with microvilli, cilia, and long zonula adherens. The features of this tumor, e.g. its superficial location, mixed giant cells, perivascular pseudorosettes or papillaries, complicated its differentiation from rhabdoid/papillary meningioma. However, immunohistochemistry and electron microscopy confirmed the diagnosis of ependymoma. The giant cell variant should be included in the subclassification of the ependymoma.

Giant cell ependymoma of the spinal cord. Case report and review of the literature

Several rare histological variants of ependymoma have been described. The authors report on a patient in whom cervical spinal cord astrocytoma was originally diagnosed after evaluation of a limited biopsy specimen. More abundant tissue obtained during gross-total resection included areas of well-differentiated ependymoma. The histological features of the tumor were extremely unusual, with a major component of pleomorphic giant cells. Its histological, immunohistochemical, and electron microscopic features, however, were consistent with ependymoma. Only two cases of terminal filum and two of supratentorial giant cell variant of ependymoma have been reported. To the authors' knowledge, this represents the first case of giant cell ependymoma of the spinal cord. The clinical significance is the potential for misdiagnosis with anaplastic (gemistocytic) astrocytoma, especially in cases in whom limited biopsy samples have been obtained.

Epithelioid ependymoma: a new variant of ependymoma: report of three cases

OBJECTIVE

To describe the pathological features of three very similar and unusual primary central nervous system tumors that are not readily recognized as conventional ependymomas but which, by ultrastructural examination, have an ependymomatous character.

METHODS

Three distinctive tumors were found in a review of our files for cases of ependymoma. In each case, hematoxylin and eosin-stained sections were reviewed, and immunostains for epithelial membrane antigen, cytokeratin, vimentin, and glial fibrillary acidic protein were performed on formalin-fixed, paraffin-embedded sections. Electron microscopy was performed in each case.

RESULTS

The tumors had a diffuse myxoid background, often containing tightly clustered cells that mimicked multinucleated giant cells, but lacking perivascular pseudorosettes or central lumen rosettes. Glial fibrillary acidic protein and vimentin immunostains did not reveal perivascular processes. Epithelial membrane antigen immunostains showed a dot-like cytoplasmic immunoreactivity in some cell clusters in two of the three cases. Cytokeratin was negative in all three cases. However, ultrastructurally, the cells of each tumor had extensive surface microvilli; the giant cell-like clusters had cells with extensive close appositions, some junctions, and, in two cases, lumina with microvilli. Two of the patients were adults (both with temporal lobe tumors), and one patient was 13 years old and had a cervical spinal cord intramedullary tumor. Each tumor was sharply circumscribed from adjacent central nervous system tissue but was not encapsulated. One of the cases in an adult was mitotically highly active; this tumor recurred locally 4 years after initial gross total excision.

CONCLUSION

These tumors are unusual variants of ependymoma. This pattern of ependymoma is sufficiently distinctive to be recognized in hematoxylin and eosin stains once the architecture of the epithelioid clusters is appreciated.

Highly anaplastic extraventricular ependymoma arising in an adult, mimicking metastatic adenocarcinoma with heavy stromal inflammation and emperiporesis

We report a case of extraventricular ependymoma arising in a 50-year-old woman that took an aggressive clinical course with recurrence three times. The initial tumor was a well-circumscribed nodule in the right temporal white matter measuring 2 cm in diameter. It showed variegated histological findings mimicking metastatic adenocarcinoma: an epithelioid arrangement of highly pleomorphic cells with pseudopapillary structures and perivascular pseudorosettes, and bizarre multinucleated giant cells with occasional emperiporesis surrounded by abundant mononuclear inflammatory cells, as well as a focal small area of conventional ependymoma. Emperiporesis and abundant mononuclear cell infiltration were not previously described in an ependymoma. The recurrent tumors predominantly showed an epithelioid pattern with frequent formation of astroblastoma-like pseudopapillary structures. Neoplastic cells were markedly atypical and had characteristic intracytoplasmic eosinophilic inclusion bodies. Much of the cells in both the initial and recurrent tumors showed a positive immunostaining for glial fibrillary acidic protein (GFAP) with accentuation to the cytoplasmic processes of the pseudorosettes and pseudopapillary structures. Epithelial membrane antigen (EMA) highlighted the epithelial differentiation of the tumor cells, while cytokeratin was completely negative. Although this tumor might be classified to at least WHO grade III from the histology and aggressive behavior, the exact grading is still controversial because of the rarity of such cases.

The immunophenotype of ependymomas

The morphologic distinction of ependymomas with epithelial cytology from metastatic carcinoma may pose a significant problem in differential diagnosis. The known presence of keratin in glioma cells further complicates the issue. Using the labeled streptavidin-biotin method with automated staining, we studied epithelial and glial marker expression in 52 ependymomas of varying type and grade, including 20 epithelial-appearing, 14 glial-appearing, eight mixed pattern, and 10 myxopapillary tumors; 38 were low grade and 14 anaplastic. All tumors were immunoreactive for glial fibrillary acidic protein (GFAP), and S-100 protein. Diffuse staining for GFAP was noted in glial-appearing ependymomas featuring perivascular pseudorosettes. Diffuse immunostaining for S-100 protein was seen in cellular lesions exhibiting epithelial-like features. Staining was more diffuse for GFAP than S-100 protein in anaplastic ependymomas. Keratin (AE1/AE3) reactivity was seen in 98% of cases, the pattern being similar to that of GFAP. The frequency of staining for other keratins varied: wide-spectrum keratin (35%), cytokeratin (CK)7 (20%), CAM 5.2 (19%), CK903 (14%), and CK20 (8%); as a rule, it was scant and limited to occasional cells and processes. epithelial membrane antigen (EMA) staining was seen in 36% of all cases and in 67% of epithelial-appearing tumors wherein it often high-lighted microlumina. Aside from AE1/AE3 staining and very infrequent wide-spectrum keratin and EMA reactivity, expression of epithelial markers was not seen in anaplastic ependymomas. No carcinoembryonic antigen (CEA) positivity was noted in any case. Collagen IV reactivity was limited to tumor cell-stroma interfaces. Although variable, S-100 protein and GFAP staining is seen in all ependymomas, particularly in true and perivascular pseudorosettes. Widespread reactivity for keratin AE1/AE3 corresponds closely to the pattern of GFAP staining. Significant staining for other keratins or for CEA is inconsistent with a diagnosis of ependymoma. EMA reactivity is largely limited to luminal staining of rosettes and tubules.