Ependymoma: Ultrastructural Studies of Two Cases

Several unusual ultrastructural findings in two ependymomas are reported. In case 1, a grade I ependymoma of the fourth ventricle, there were rosettes, perivascular pseudorosettes, and tumor cells having unusual intracytoplasmic vacuoles by light microscopy. Ultrastructurally, these vacuoles were frequently microrosettes as well as scattered, degenerated cytoplasmic processes of tumor cells. The lumina of some of the microrosettes were bordered by abnormally long and malformed zonulae adherentiae. In case 2, a recurrent grade III ependymoma of the third ventricle, there were rosettes and perivascular pseudorosettes as well as more cellular and anaplastic areas by light microscopy. Ultrastructurally, the cytoplasmic processes of tumor cells in perivascular pseudorosettes contained frequent dense-core vesicles and occasional parallel arrays of microtubules. These structures do not occur in normal mammalian ependymal cells but do occur in the ependymal tanycyte, a related cell that is plentiful in the walls of the third ventricle. Thus some of the tumor cells of this third ventricle ependymoma appear to have differentiated as tany-cytes.     

Extraspinal ependymoma of the broad ligament

Extraspinal ependymoma is a rare tumor, occurring most commonly in the sacrococcygeal region, and only a small number of cases have been reported to arise in the uterine ligament. Herein is reported a case of extraspinal ependymoma arising in the broad ligament of a 27‐year‐old woman. The lesion was 14 cm in diameter with an intra‐abdominal implant in the omentum. On cut section the tumor was found to be solid, and demonstrated hemorrhaging, necrosis, myxoid foci, and central cystic spaces. Microscopically the tumor was composed of a proliferation of short spindle or polygonal cells arranged in short fascicles or in a solid sheet‐like fashion with occasional perivascular pseudorosettes, together with myxoid areas and variable histological architectures exhibiting cribriform, pseudopapillary, and variable‐sized cystic patterns. On immunohistochemistry most tumor cells were positively reactive to glial fibrillary acidic protein (GFAP), CD99, estrogen receptor, and progesterone receptor. The patient has remained disease‐free for 6 months after the adjuvant chemoradiotherapy. Extraspinal ependymoma should be considered as a differential diagnosis when examining unusual intrapelvic tumors, especially in young female patients. The identification of characteristic histological features such as perivascular pseudorosettes and immunohistochemical expression of GFAP are helpful for confirming the diagnosis.     

Ependymoma: Ultrastructural Studies of Two Cases

Several unusual ultrastructural findings in two ependymomas are reported. In case 1, a grade I ependymoma of the fourth ventricle, there were rosettes, perivascular pseudorosettes, and tumor cells having unusual intracytoplasmic vacuoles by light microscopy. Ultrastructurally, these vacuoles were frequently microrosettes as well as scattered, degenerated cytoplasmic processes of tumor cells. The lumina of some of the microrosettes were bordered by abnormally long and malformed zonulae adherentiae. In case 2, a recurrent grade III ependymoma of the third ventricle, there were rosettes and perivascular pseudorosettes as well as more cellular and anaplastic areas by light microscopy. Ultrastructurally, the cytoplasmic processes of tumor cells in perivascular pseudorosettes contained frequent dense-core vesicles and occasional parallel arrays of microtubules. These structures do not occur in normal mammalian ependymal cells but do occur in the ependymal tanycyte, a related cell that is plentiful in the walls of the third ventricle. Thus some of the tumor cells of this third ventricle ependymoma appear to have differentiated as tany-cytes.     

Rapid spontaneous malignant progression of supratentorial tanycytic ependymoma with sarcomatous features – “Ependymosarcoma”

By analogy to gliosarcoma, the term “ependymosarcoma” has recently been coined to thematize the rare phenomenon of a malignant mesenchymal component arising within an ependymoma. We report on an example of this paradigm, involving tanycytic ependymoma as the host tumor in a 40-year-old female who underwent two tumor extirpation procedures at one-year interval. She first presented with severe headaches, and was seen by imaging to harbor a moderately enhancing mass 2.5 cm in diameter at the rostral septum pellucidum accompanied by occlusive hydrocephalus. Microscopically, the tumor consisted of solid, wavy fascicles of elongated cells that were occasionally interrupted by vague perivascular pseudorosettes. Mitotic activity was absent, and less than 1% of nuclei immunoreacted for MIB-1. A histological diagnosis of tanycytic ependymoma (WHO grade II) was rendered, and no adjuvant therapy given. At recurrence, the lesion was 3.5 cm in diameter, intensely enhancing, and had already seeded into the subarachnoid space. Histology showed a biphasic glial–sarcomatous architecture with remnants of the original ependymoma now displaying hypercellularity and atypical – yet not frankly anaplastic – features. The sarcomatous moiety consisted of spindle and epithelioid cells densely interwoven with reticulin fibers. While the ependymal component was GFAP and S100 protein positive, and featured punctate staining for EMA, none of these markers was expressed in the adjacent sarcoma. Instead, the latter reacted for vimentin and smooth muscle actin. To the best of our knowledge, this is the first documentation of tanycytic ependymoma undergoing malignant transformation, one driven by a highly anaplastic mesenchymal component, corresponding to “ependymosarcoma”.     

Myxopapillary ependymoma with anaplastic features

A case of myxopapillary ependymoma with anaplastic features in 15-year-old boy is reported. The tumor was located in the intradural space extending to the 12th thoracic to 2nd lumbar vertebral level. It was excised with the accompanying spinal arch of the T12 to L2 vertebra. At operation, the tumor was not attached to the surrounding soft and bony tissues. The tumor, measuring 49 x 19 x 15 mm, was brownish-yellow in color and involved the conus medullaris and filum terminale. Histologically, the tumor was composed of biphasic features of a hypercellular papillary growth area and a hypocellular myxoid area. In the papillary growth area, ependymal rosettes and perivascular pseudorosettes were observed. These findings were consistent with those of a myxopapillary ependymoma, although multiple foci of punctate necrosis within the tumor and proliferation of endothelial cells showing glomeruloid structures were observed. Many mitotic figures were also observed. In addition, the Ki-67 labeling index of tumor cells was 10.1%. These findings are unusual for myxopapillary ependymoma, and therefore, it appeared that the diagnosis of myxopapillary ependymoma with anaplastic features was appropriate.     

Ovarian ependymoma

A 76-year-old woman presented with a large calcifying mass behind the bladder. The tumor contained solid areas of a yellowish white color. Microscopic examination revealed highly cellular solid areas with many typical ependymal perivascular pseudorosettes. The cells contained uniform round-to-oval nuclei, some of which had irregular contours, clumped chromatin and occasional prominent nucleoli. There was widespread geographic necrosis and there were 5 atypical mitotic figures per 10 high power fields. Glial fibrillary acidic protein (GFAP) immunopositivity was observed in the cytoplasm of the tumor cells. Based on the histopathologic and immunohistochemical features, the tumor was diagnosed as an anaplastic ependymoma. This is to the best of our knowledge only the second case of anaplastic ependymoma in the medical literature.     

Giant cell ependymoma-report of three cases and review of the literature

Ependymomas constitute the most common type of primary spinal cord tumors, and are subclassified as myxopapillary ependymoma, classic ependymoma, and anaplastic ependymoma. Ependymomas can be further subclassified based on morphologic phenotype: cellular, papillary, tanycytic, clear cell, pigmented and epithelioid. Giant cell ependymoma (GCE), a rare variant, has recently been described. Reported cases have exhibited a wide anatomic distribution, including spinal cord, cerebrum and cerebellum. We report here three cases of GCE, arising from cerebrum in a 5-year-old girl, spinal cord in a 34-year-old female and cerebellum in an 86-year-old female respectively. Histologically those cases showed prominent pleomorphic giant cells with focal perivascular pseudorosettes in all cases. Tumor cells were immunopositive for GFAP and EMA. Only the first case was qualified for anaplastic ependymoma. No recurrence was noted in these three cases after 57, 46 and 6 months of follow-up respectively. By reviewing the literature, GCEs arising from spinal cord and cerebellum tended to have low-grade morphology while supratentorially located GCEs tended to have anaplastic features. GCEs were preferentially located in extraventricular regions. Anaplastic GCEs in adult population seemed to pursue a more aggressive behavior. Gross total resection should still be the main treatment for GCEs.     

Clear-cell Ependymoma of the Cerebellum: A Case Report

A case of clear-cell ependymoma occurring in the cerebellum of a 3-year-old girl is reported. Light-microscopically, the tumor consisted mainly of clear cells with a perinuclear halo and showed some vague perivascular pseudorosettes, not true rosettes. In addition, the histological features of anaplasia, characterized by increased mitosis and focal pseudopalisading necrosis, were also observed. Immunohistochemically, the tumor cells were focally positive for glial fibrillary acidic protein and weakly positive for epithelial membrane antigen. Ultrastructurally, the intermediate junctions and rudimentary cilia confirmed the ependymal differentiation. Fifteen cases of infratentorial clear-cell ependymoma have been reported to date, and this case is the second childhood tumor among them, to the best of the authors' knowledge.     

cIMPACT‐NOW update 7: advancing the molecular classification of ependymal tumors

Advances in our understanding of the biological basis and molecular characteristics of ependymal tumors since the latest iteration of the World Health Organization (WHO) classification of CNS tumors (2016) have prompted the cIMPACT‐NOW group to recommend a new classification. Separation of ependymal tumors by anatomic site is an important principle of the new classification and was prompted by methylome profiling data to indicate that molecular groups of ependymal tumors in the posterior fossa and supratentorial and spinal compartments are distinct. Common recurrent genetic or epigenetic alterations found in tumors belonging to the main molecular groups have been used to define tumor types at intracranial sites; C11orf95 and YAP1 fusion genes for supratentorial tumors and two types of posterior fossa ependymoma defined by methylation group, PFA and PFB. A recently described type of aggressive spinal ependymoma with MYCN amplification has also been included. Myxopapillary ependymoma and subependymoma have been retained as histopathologically defined tumor types, but the classification has dropped the distinction between classic and anaplastic ependymoma. While the cIMPACT‐NOW group considered that data to inform assignment of grade to molecularly defined ependymomas are insufficiently mature, it recommends assigning WHO grade 2 to myxopapillary ependymoma and allows grade 2 or grade 3 to be assigned to ependymomas not defined by molecular status.     

Clear-cell ependymoma of the cerebellum: a case report

A case of clear-cell ependymoma occurring in the cerebellum of a 3-year-old girl is reported. Light-microscopically, the tumor consisted mainly of clear cells with a perinuclear halo and showed some vague perivascular pseudorosettes, not true rosettes. In addition, the histological features of anaplasia, characterized by increased mitosis and focal pseudopalisading necrosis, were also observed. Immunohistochemically, the tumor cells were focally positive for glial fibrillary acidic protein and weakly positive for epithelial membrane antigen. Ultrastructurally, the intermediate junctions and rudimentary cilia confirmed the ependymal differentiation. Fifteen cases of infratentorial clear-cell ependymoma have been reported to date, and this case is the second childhood tumor among them, to the best of the authors' knowledge.     

Case of clear cell ependymoma of medulla oblongata: clinicopathological and immunohistochemical study with literature review

Clear cell ependymoma has been included in the WHO classification of the central nervous system in 1993, after the first report by Kawano et al. Since then, only a few cases have been reported. Most clear cell ependymoma cases reported in the literature so far were located in the supra-tentorial compartment and/or cerebellum, and one case was in the cervical spinal cord. We report a case of clear cell ependymoma whose histological features were sufficient for the diagnosis and was unusually located in the fourth ventricle originating from the medulla oblongata. The tumor showed uniform tumor cells with perinuclear halo, nuclei being centrally located. Most of the tumor cells were arranged as perivascular pseudorosettes, and no ependymal canals or rosettes were evident. Mitotic figures were not frequent. Immunohistochemically, the tumor cells were strongly reactive for glial fibrillary acidic protein and vimentin, and weak and dot-like positive for epithelial membrane antigen. Clear cell change of the tumor cells appeared to be fixation artifact because this feature was not evident in the frozen section.     

Astroblastoma: a distinct tumor entity characterized by alterations of the X chromosome and MN1 rearrangement

Astroblastoma is a rare, enigmatic tumor of the central nervous system (CNS) which shares some clinicopathologic aspects with other CNS tumors, especially ependymoma. To further clarify the nature of astroblastoma, we performed clinicopathologic and molecular genetic studies on eight cases of astroblastoma. The median age of the patients was 14.5 years, ranging from 5 to 60 years, and seven of the patients were female. All tumors arose in the cerebral hemisphere and radiologically appeared to be well‐bordered, nodular tumors often associated with cystic areas and contrast‐enhancement. Six of the seven patients with prognosis data survived without recurrences during the follow‐up periods ranging from six to 76 months. One patient had multiple recurrences and died six years later. All tumors exhibited salient microscopic features, such as being well demarcated from the surrounding brain tissue, perivascular arrangement of epithelioid tumor cells (represented by “astroblastic” pseudorosettes, trabecular alignment, and pseudopapillary patterns), and hyalinized blood vessels. Immunoreactivity for GFAP, S‐100 protein, Olig2, and EMA was variably demonstrated in all tumors, and IDH1 R132H and L1CAM were negative. Array comparative genomic hybridization revealed numerous heterozygous deletions on chromosome X in the four tumors studied, and break‐apart fluorescence in situ hybridization demonstrated rearrangement of MN1 in five tumors with successful testing. The characteristic clinicopathologic and genetic findings support the idea that astroblastoma is distinct from other CNS tumors, in particular, ependymoma. In addition, MN1 rearrangement and aberrations of chromosome X may partly be involved in the pathogenesis of astroblastoma.     

Ultrastructural Pathology of Anaplastic and Grade II Ependymomas reveals Distinctive Ciliary Structures – Electron Microscopy Redux

Ependymoma tumors likely derive from the ependymal cells lining the CNS ventricular system. In grade II ependymomas, tumor cells resemble typical ependymocytes, while anaplastic ependymomas are poorly differentiated. We studied three grade II and one anaplastic ependymoma, focusing on the ciliary structures. To unambiguously characterize the ultrastructure and number of cilia, we performed electron microscopy serial section analysis of individual cells. Differentiated ependymomas contained large basal bodies and up to three cilia, and lacked centrioles. Anaplastic ependymoma cells showed instead two perpendicularly oriented centrioles and lacked cilia or basal bodies. These findings could contribute to understand the mechanisms of ependymoma aggressiveness.     

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.     

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.     

Ectopic cervical anaplastic ependymoma

Ependymomas generally arise in the central nervous system (CNS), although rare primary extraneural ependymomas have been observed. Reported herein for the first time is the case of a patient with primary ectopic cervical anaplastic ependymoma. The tumor was found in the right neck root region of a 35-year-old man. No additional tumor was found in the CNS or in other parts of the body. The patient received surgery and post-surgical local radiotherapy. Microscopically, the tumor consisted of round to oval cells with fine chromatin, distinct nucleoli, moderate nuclear atypia and numerous mitoses (>25/10 high-power fields) in a densely cellular growth pattern with characteristic fibrillary cytoplasm and formation of perivascular pseudorosettes. By immunohistochemistry, the tumor cells were positive for glial fibrillary acidic protein, epithelial membrane antigen (EMA), vimentin and S-100 protein. EMA staining showed a membranous as well as a paranuclear pattern of immunoreactivity. Electron microscopic studies revealed that tumor cells form micro rosettes, into which microvilli and cilia projected. The diagnosis was World Health Organization grade III anaplastic ependymoma. There is no evidence of local tumor recurrence or distant metastasis after 30 months follow up. The present case adds yet another unique example to the already diverse spectrum of head and neck neoplasms encountered in surgical pathology.     

伸展细胞型室管膜瘤的临床病理特点

目的：观察一少见的特殊类型室管膜瘤的临床病理特点,拟译名为伸展细胞型室管膜瘤。方法：复习3例此型的临床病理和免疫组化资料及有关文献。结果：3例肿瘤均位于脊髓内。它们的临床表现和放射影像学与室管膜瘤其他类型表现相同,病理形态学上,瘤细胞呈现双极的长梭形胶质细胞,形成不典型的血管周菊形团,GFAP、EMA弱阳性,而vimentin强阳性,而可与星形细胞瘤及神经鞘瘤相鉴别,其预后与其他类型室管膜瘤相类似。结论：由于肿瘤由双极、长梭形细胞组成。及tanycyte来源于tanyos有stretch伸出展开之意,“tanycytic ependymona ”以译成“伸展细胞型室管膜瘤”为妥。     

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.     

Myxopapillary ependymoma: cytomorphologic characteristics and differential diagnosis

Myxopapillary ependymoma (ME) is a rare tumor with a predilection for sacrococcygeal area of adults. We present the cytomorphology of one such case in a 21-yr-old man, diagnosed by fine-needle aspiration (FNA). The tumor disclosed biphasic morphology with nests and aggregates of epithelioid malignant cells as well as branching cords of myxohyaline material. Most noticeable was the presence of distinct hyaline globules surrounded by neoplastic cells. The differential diagnosis of ME includes chordoma, adenoid cystic carcinoma, mucinous adenocarcinoma, and germ cell tumor. An accurate preoperative diagnosis of ME on FNA can be achieved based on its distinctive cytomorphologic features.     

Ependymal variant of dysembryoplastic neuro-epithelial tumor

Dysembryoplastic neuro-epithelial tumors (DNET) are glioneuronal tumors with a common astrocytic or oligodendroglial differentiation. We report a case of DNET with an ependymal differentiation. A 13 years-old girl had refractory focal seizures for 3 years. Successive MRI showed a stable cortical lesion of the right temporal lobe with DNET characteristics. The lesion was resected. Histological examination revealed a pure ependymal differentiation characterized by perivascular pseudorosettes containing EMA immunoreactive cells. Mib1 positive cells were absent. In spite of histologic features of ependymoma, this tumor showed clinical, radiological and behaviour characteristics of DNET. We are not aware of any other case of DNET with ependymal differentiation in the literature. Our observation suggests that the glial component of DNET may show an ependymal differentiation.