A rare subtype of meningioma: Case series of anaplastic meningioma and review of the literature

RATIONALE

Anaplastic meningioma, a rare subtype of meningioma, has malignant morphological characteristics and a World Health Organization (WHO) grade of III.

PATIENT CONCERNS

In this report, we present findings from 6 cases of anaplastic meningioma.

DIAGNOSES

Pathological examination of the tumors, including hematoxylin and eosin staining and immunohistochemical staining, was performed. Of the six cases of anaplastic meningioma, two were recurrent tumors from original seminoma with a WHO grade of I. Histologically, three cases had carcinoma-like morphology, one case had sarcoma-like morphology, and two had two kinds of tissue structures: carcinoma-like tumor cell nests and areas with spindle tumor cells. Necrosis was detected in most cases (5/6). Ki67 index was high and varied from 20% to 70%.

INTERVENTIONS

All the patients received surgery. 3 patients received adjuvant radiotherapy. 1 patient received chemotherapy.

OUTCOMES

4 patients had no recurrence at follow-up of 19, 30, 46 and 54 months after the last surgery. 1 patient had recurrence 3 months after the last surgery. 1 patient died 12 days after the last surgery.

LESSONS

This malignant subtype can be secondary to a WHO grade I meningioma after a long quiescent period. Necrosis was common in the tumor tissues, and Ki67 index was usually high. For patients with a history of meningioma, including benign cases, regular physical examination is important for early detection of tumor recurrence and malignant transformation.

Ultrastructure of meningiomas: autophagy is involved in the pathogenesis of "intranuclear vacuoles"

We report here common ultrastructural findings in a short list of meningiomas. At the lower power magnification, a tumour consisted of elongated or round cells and innumerable cellular processes connected with diverse intercellular junctions. Nuclei presented no specific features, nucleoli were infrequently seen and heterochromatin was clumped beneath the nuclear membranes. In a case of clear cell meningioma, cells were of watery cytoplasm. Occasionally, immobile cilia, completely ensheathed by the cytoplasm and anchored by blepharoplasts were seen; as we did not encounter those rare cilia in cross-sections, no further insight into their inner microtubular-doublet structure was possible. The cytoplasm of the cells and the processes were filled with the intermediate filaments. In the intercellular space, collagen fibrils and electron-dense material was occasionally observed. The majority of the tumour samples were filled with processes. Several types of junctional complexes were observed. The most frequent were desmosomes and in the proper plane of section their whole pentalaminar structure was readily discernible. However, robust tonofilaments, as seen in epithelial neoplasms, were not observed. Those desmosomal junctions were either completely symmetric or asymmetric, but the exact symmetry could not be judged without the assistance of a goniometer. Some junctional complexes were more elaborate, with desmosomal junctions separated by a tight apposition of membranes, which suggests tight junctions. "Intranuclear vacuoles" well-visible even at low power were defined as indentation of the cytoplasm into the nucleus. Within these vacuoles, autophagic vacuoles and lysosomal bodies were seen, suggesting an active macroautophagy process. In 2 cases, severe lipidization of meningioma cell cytoplasm was observed. In a case of anaplastic meningioma, a mitotic figure was found. In another case, empty rectangular spaces in the cytoplasm, suggestive of pre-existing crystalloid structures, were seen.

An Ultrastructural and Immunohistochemical Study of Microcystic Meningioma with Emphasis on Matrix Proteins and Connexin 26 Type Gap Junctions

Although the histopathological subtypes of meningioma do not themselves appear to have prognostic significance, they are collectively important for defining the overall histopathological entity of microcystic meningioma (MCM) and allowing a distinction from other intracranial tumors, such as capillary hemangioblastoma, glioma, and metastatic renal cell carcinoma showing similar histology. Four cases of MCM were analyzed by conventional histology, immunohistochemistry, and electron microscopy. The present series of MCM was characterized by spindle- or cobweb-shaped tumor cells, characteristically associated small blood vessels, and a peculiar microcystic pattern. Among the microcystic meningeal tumor tissue, small areas of conventional subtypes were identified. Immunohistochemically, tumor cells showed the mesenchymal features of vimentin positivity and a rich distribution of matrix proteins around tumor cells. They lacked epithelial marker positivity but were faintly EMA positive. Ultrastructurally, primitive cellular junctions, desmosomes, and gap junctions were frequently seen between tumor cells. The gap junctions correlated with connexin 26 immunoreactivity. Although lacking an obvious epithelial nature, these features could be interpreted as showing an abortive differentiation mimicking meningothelial (arachnoidal) cells, which, physiologically, regulate cerebrospinal fluid between blood vessels and brain parenchyma.

Ultrastructural profile of microcystic meningioma

OBJECTIVE

Microcystic meningioma was originally classified as a subtype of meningioma by the World Health Organization classification of brain tumours in 1993, and accounts for 1.6% of intracranial meningiomas. This subtype is a variety of meningioma in which micro- and macro-cysts are diffuse. The morphologic characteristics are well defined, while the histogenetic mechanism that give rise to these patterns remain unclear.

MATERIALS AND METHODS

The authors present an electron microscopic study of an unusual case of fronto-temporal microcystic meningioma, manifesting as history of headache, right paresis and dysphasia in a 73-year-old female. Computer tomography revealed a large hypodense mass in the left fronto-temporal region, with slight contrast enhancement.

RESULTS

Ultrastructural observation showed complex alterations among small vessels and intratumoral capillaries in a background of severe modification in vessel permeability.

CONCLUSIONS

This electronic microscopy study documented that growth of the cyst was due not only to accumulation of in extracellular fluid, but also to cytolysis consequent to ingravescent hydropic degeneration.

Microcystic meningioma in a dolphin (Delphinus delphis): immunohistochemical and ultrastructural study

A wild common dolphin was found stranded on the French Atlantic coast. At necropsy, an intracranial grey- to tan-coloured mass (7 x 5 x 4 cm) was found at the right cerebellopontine angle, compressing the right cerebellar hemisphere, the brainstem and the occipital lobe of the right cerebral hemisphere. Microscopically, the tumour was composed of small lobules of polygonal to elongated neoplastic cells with multifocal areas of stellate and vacuolated cells. Neoplastic cells strongly expressed vimentin, S-100 protein and neuron-specific enolase. They were rarely positive for cytokeratin. Ultrastructurally, the neoplastic cells displayed all the diagnostic features of meningiomas and in some areas showed long cytoplasmic processes delimiting extracellular spaces. The immunohistochemical and ultrastructural features were consistent with the histopathological diagnosis of a microcystic meningioma. This is the first report of a meningioma in dolphins or in any other cetacean species.

Meningeal melanocytoma

BACKGROUND

Meningeal melanocytoma was first described over 30 years ago as a benign tumour derived from melanocytes. Since then, data suggest that its mode of presentation is variable without a clear predilection for any particular site in the neuroaxis. Although classified as a benign tumour, this tumour shows a marked tendency towards reduced survival following subtotal resection and transformation over time in a limited number to malignant melanoma. Incomplete resection of these tumours without postoperative radiotherapy has only a 42% 5-year survival rate. Its classification as a benign tumour should be revised, given the published 5-year survival data.

ILLUSTRATIVE CASE

We report a fatal case of meningeal melanocytoma in the cerebello-pontine angle in a 10-year-old child. This case exemplifies the vascular nature of these lesions even with minimal vascular blush on angiography. An updated literature search is presented, the results of which highlight the need for close follow-up and adjuvant treatment following subtotal resection.

Intracerebral schwannoma clinically and radiologically mimicking meningioma

A case of intracerebral schwannoma (ICS) occurring in a 33-year-old woman is presented. The patient's history of headache, numbness, tingling and the recent development of weakness of the right upper extremity with right facial droop began during pregnancy. Magnetic resonance imaging (MRI) showed a 4 x 2 x 2 cm heterogeneous, gadolinium-enhanced mass at the left frontoparietal junction, with peritumoral edema and a dural-based attachment. During her pregnancy, the mass increased in size. The surgically resected specimen consisted of lobulated, somewhat gelatinous soft tissue. Microscopically, the tumor demonstrated classic biphasic Antoni type A and B patterns, admixed with degenerative changes. Immunohistochemically, the neoplastic cells were positive for S-100 protein (diffuse and strong), CD34 (primarily in Antoni B areas), glial fibrillary acidic protein (GFAP; weak and diffuse) and calretinin (mainly in Antoni A areas), while none was positive for CD31, estrogen and progesterone receptors, bcl-2, or epithelial membrane antigen (EMA). Ultrastructurally, basal laminae and Luse bodies were identified. The differential diagnosis includes fibrous meningioma, solitary fibrous tumor, and ICS. Twenty-seven cases of ICS were reviewed in which the histological diagnosis was confirmed immunohistochemically or ultrastructually, and the cases were summarized (including the present case). A combined use of immunostains (S-100 protein, EMA, CD34, and maybe calretinin) is of great help in distinguishing ICS from its histological mimickers.

Primary chordoid meningioma of lung

Primary meningiomas of the lung are rare. Most pulmonary meningiomas are typical syncytial or transitional meningiomas with smaller numbers of fibrous-type tumors. Herein, we report an unusual pulmonary tumor with the microscopic, immunohistochemical, and ultrastructural characteristics of a chordoid meningioma. The tumor was composed of cords and fascicles of small- to medium-sized spindle and epithelioid cells with eosinophilic cytoplasm and round nuclei with finely dispersed chromatin. The tumor cells were surrounded by an abundant mucoid, vacuolated stroma. The periphery of the tumor was enveloped by a significant lymphoplasmacytic infiltrate. The neoplastic cells were positive for vimentin and epithelial membrane antigen only. The unusual morphology of the tumor caused significant diagnostic difficulties. The differential diagnosis included inflammatory myofibroblastic tumor, spindle cell myoepithelioma, and extraskeletal myxoid chondrosarcoma. To the best of our knowledge, this is possibly the first description of an extracranial or intrapulmonary chordoid meningioma.

Meningioma with eosinophilic granular inclusions

Rare meningiomas have been described that contain eosinophilic inclusions that have a granular or granulofilamentous ultrastructure. We describe a 66-year-old woman who developed a planum sphenoidale meningioma. Histologically, the tumor was composed of meningothelial cells arranged in fascicles and whorls, typical of a well-differentiated meningioma. Many tumor cells contained round intracytoplasmic eosinophilic inclusions that were periodic acid Schiff-negative and red on Masson trichrome. The inclusions were immunopositive for vimentin, and were immunonegative for epithelial membrane antigen, smooth muscle actin, desmin and type IV collagen. Ultrastructural examination showed the inclusions were composed of round to oval, well-demarcated, non-membrane-bound, osmiophilic granular material. The inclusions within this tumor had histochemical, immunohistochemical and ultrastructural properties not described in other reported meningiomas with eosinophilic granular or granulofilamentous inclusions.

Sclerosing meningioma: immunohistochemical analysis of five cases

Sclerosing meningioma is a rare morphologic subtype of meningioma and may be mistaken for atypical or malignant meningioma and astrocytoma or schwannoma because of marked collagen deposits and a sparse population of cells with little resemblance to meningothelial cells. Authors describe the histopathologic and immunophenotypic features of five cases of sclerosing meningioma. Histologically, all the cases consisted of paucicellular collagenous tissue containing spindle cells with or without small foci of meningothelial cell proliferation. The morphology and immunohistochemical profile of the spindle cells were different from those of conventional meningothelial cells. The meningothelial cells showed a typical immunoreactivity of conventional meningiomas, while the spindle cells displayed a strong expression of vimentin. The Ki-67 labelling index was uniformly low in all cases, and none of cases expressed p53 protein. In summary, the recognition of meningothelial cells in massively sclerotic lesions is helpful for a correct diagnosis. In the cases with a total absence of meningothelial cells, however, the vague collagenous whorls are more diagnostic rather than immunohistochemistry. Considering association with clear cell meningioma, prospective and retrospective long-term follow-up is necessary for deciding whether reminiscent clear cell meningiomas should be separated from sclerosing meningioma or not.

Melanocytic colonization of a meningothelial meningioma: histopathological and ultrastructural findings with immunohistochemical and genetic correlation: case report

OBJECTIVE AND IMPORTANCE

Melanocytic colonization of nonpigmented extracranial tumors has been reported in adenocarcinomas, squamous cell carcinomas, skin appendage tumors, and dermatofibrosarcoma protuberans. To our knowledge, melanocytic colonization of a meningioma has not previously been described.

CLINICAL PRESENTATION

We report an unusual case of a 70-year-old African-American woman who presented with a large frontoparietal meningioma that extended through the calvarium.

INTERVENTION

Craniotomy with gross total resection of the tumor was performed. Histochemistry, immunocytochemistry, ultrastructural analysis, and molecular genetic study via fluorescence in situ hybridization confirmed melanocytic colonization of a meningothelial meningioma.

CONCLUSION

With the inclusion of meningothelial meningioma, the spectrum of tumors affected by melanocytic colonization continues to expand.

Meningioma with extensive noncalcifying collagenous whorls and glial fibrillary acidic protein expression: new variant of meningioma diagnosed by smear preparation

The purpose of this report is to describe the unique cytological findings of a new recently characterized type of meningioma that has extensive noncalcifying collagenous whorls and glial fibrillary acid protein (GFAP) expression. This new entity, described by Haberler and colleagues, was named whorling sclerosing variant of meningioma. The patient was a 34-yr-old white man with a large tumor in the brainstem. Intraoperative smear preparations showed a tumor with a large number of solid hyaline masses in a loose background and in focal areas tumor cells formed cohesive nests with a somewhat whorling appearance. The histological sections showed a neoplasia composed of innumerable eosinophilic, collagenous, noncalcified round deposits, cuffed by scattered meningothelial tumor cells. The neoplastic cells showed diffuse cytoplasmic reactivity for EMA and vimentin, as well as positivity to GFAP. This is the first cytological description of this new entity in the literature.

Malignant transformation of meningeal melanocytoma: A case report

Intracranial meningeal melanocytoma is an uncommon tumor that is considered benign. We formerly reported an intracranial meningeal melanocytoma. Here we report a extremely rare case of malignant transformation of this tumor. A 49-year-old man complained of a headache. Magnetic resonance scanning revealed a mass in the left frontal region. The patient underwent gross total removal of the tomor in 1994. The histological findings showed a meningeal melanocytoma. In 1998, he underwent gamma-knife surgery for local recurrence. An additional operation was performed in 1999 became tumor growth was not stopped. The tumor was partially excised by left frontal craniotomy. Histopathological examination revealed a malignant melanoma originating from a melanocytoma. The tumor was composed of a proliferation of severely atypical melanocytoid cells with slightly irregular nuclei and prominent nucleoli, associated with necrosis and hemorrhage. Mitotic figures were encountered occasionally. After six months, he died from cerebrospinal fluid dissemination of this tumor. To our knowledge, this is the first report of malignant transformation of an intracranial meningeal melanocytoma.

Giant-cell tumor of bone arising from the falx cerebri. A case report

The histological and ultrastructural features of a giant-cell tumor of bone arising in the falx cerebri of a 27 year-old man are described. The tumor was embedded in the medial aspect of the left frontal lobe and was not attached to any of the bones of the skull. At surgery, the tumor was lightly adherent to the falx and was easily extracted. Histologically, the tumor was composed of mononuclear spindle-shaped and ovoid stromal cells, multinuclear giant cells containing 20-30 nuclei, and foci of osteoid and bone production. Hemorrhagic and cystic areas were also present within the tumor. Ultrastructurally, the spindle-shaped cells resembled fibroblasts and were surrounded by small bundles of collagen fibrils. The ovoid cells contained numerous mitochondria, abundant rough endoplasmic reticulum, vesicles, lysosomes, phagosomes and osseous material in the cytoplasm suggesting their monocyte-macrophage lineage. These cells were closely apposed and displayed evidence of fusion in the form of focal and linear subplasmalemmal densities to form multinucleated giant cells with similar organelles and multiple nuclei. It is suggested that the primary giant cell tumor of the one arose from the metaplastic ossification of the falx. To our knowledge, a giant-cell tumor of bone arising from the falx cerebri has not been previously described.

Meshy meningioma: a potential novel variant

A potential novel variant of meningioma is reported. The tumor was solid, hard, white-colored, well circumscribed in a fibrous capsule and fixed to the dura, showing no invasion into the brain parenchyma. Histopathological study presented a sparsely cellular tumor composed of cells with fine reticular or mesh-like cytoplasm, each containing an oval nucleus. Mitotic figures were rarely seen. Immunohistochemical studies of tumor cells showed positive immunoreactivity for vimentin and epithelial membrane antigen but were negative for GFAP, desmin, neurofilament, keratin, S-100, CD34 and CEA. Bipolar neoplastic cells and long processes were noted on ultrastructural observation; these were attached side by side to each other by desmosomes, resulting in a mesh-like configuration. Perinuclear cytoplasm and processes were rich in intermediate filaments and rough endoplasmic reticulum. These microscopic and ultrastructural features have never before been reported among the variants of meningioma. The name 'meshy meningioma' is proposed for this novel variant.

Brain oedema in secretory meningiomas

Brain oedema is usually associated with intracranial meningiomas in about 50-66%. As underlying causes, different factors like localisation, vascular supply, angiogenic growth factors and histological subtypes are discussed, and its existence is probably multifactorial. We present 11 patients with the rare subtype of secretory meningiomas. Brain oedema was observed in 82%. These tumours are localised mainly at the frontal convexity and at the sphenoid ridge. All 11 patients were female so that hormonal factors also may play a role in the production of peritumoural oedema. The postoperative outcome was good and no recurrences were seen during follow-up.

Cytodiagnosis of a meningeal fibrosarcoma metastatic to the thyroid gland

A case of primary leptomeningeal fibrosarcoma metastatic to the thyroid gland, diagnosed by fine needle aspiration biopsy is described. The patient, a 39-year-old women was initially diagnosed with a leptomeningeal fibrosarcoma. Sections of the primary tumor studied by electron microscopy showed that the tumor cells have the ultrastructure features of a fibroblast. She underwent tumor resection, followed by chemotherapy and local radiotherapy. Four months later, she presented with dysphagia. Ultrasonography confirmed the presence of a 2-cm mass in the right lobe of thyroid. A fine needle aspiration biopsy was performed. Light microscopy showed interwoven bundles of neoplastic spindle cells similar to the primary tumor, consistent with a metastatic fibrosarcoma. To our knowledge, this is the first report of a primary meningeal fibrosarcoma that metastasized to the thyroid gland, which was diagnosed by a fine needle aspiration biopsy.

Ultrastructural examination is essential for diagnosis of papillary meningioma

AIMS

Papillary meningioma is a rare meningeal tumour. To date only a few cases have been reported and their immunohistochemical features have not been fully documented.

METHODS AND RESULTS

A 49-year-old woman presented with a 2-month history of headaches and memory disturbance. CT and MRI imaging showed an enhancing pineal mass with extension into the occipital lobes and invasion of the splenium. At surgery, the tumour was found to be tough and vascular with a well-defined capsule. No recurrence was noted 19 months after the operation. In another case a 44-year-old woman was admitted with 1-month history of headaches, poor memory, imbalance and diplopia. CT scan showed a large hyperdense, uniformly, enhancing mass within the middle cranial fossa at the petrous ridge. The tumour recurred 19 and 25 months after first resection. The histology of both tumours was similar. The neoplasms contained polygonal cells with a moderate amount of cytoplasm, rounded regular nuclei and distinct cell borders. The cells were arranged radially around the blood vessels (perivascular pattern) and a papillary pattern was seen only focally. Mitotic figures were moderately frequent. Immunohistochemistry showed that both tumours were immunoreactive to vimentin and NSE, whereas GFAP, CAM5.2, EMA, S100 protein and synaptophysin were negative. Electron microscopy revealed interdigitating cell processes, desmosomes and intermediate filaments.

CONCLUSIONS

The histological and immunohistochemical features of these two tumours are complex and difficult to interpret. Although papillary meningiomas were considered in our initial differential diagnosis, the final conclusion was possible only when the ultrastructural features were revealed.

Xanthomatous changes in atypical and anaplastic meningiomas. Light and electron microscopic investigations

Xanthomatous changes may occur in meningiomas of different histological type, however their incidence in combination with histological features of atypical or anaplastic meningioma has not been previously documented. In this report we present clinicopathologic, immunohistochemical and ultrastructural studies in the surgical cases of two atypical and three anaplastic meningiomas exhibiting prominent xanthomatous changes. In all tumors the xanthomatous cells were seen in association with typical meningioma structures such as meningothelial whorls or psammoma bodies as well as within the tumor parts displaying pleomorphism, patternless growth, increased cellularity, presence of necroses and mitoses or brain invasion. Ultrastructural study revealed a wide-range of lipid-containing cells, reflecting a continuum of gradual transition between polymorphic meningioma cells and xanthomatous cells. Commonly, the lipidized cells exhibited different degrees of plasmalemmal interdigitations and desmosomal junctions. Our study allowed us to confirm the meningothelial origin of xanthomatous cells in atypical and anaplastic meningiomas. Moreover, the ultrastructural observations of lysosomes in the majority of xanthomatous cells and the immunoreactivity for the CD68 antigen indicated their macrophage characteristics. It seems that a mixed meningeal/macrophage nature of xanthomatous cells can be related to the functional and structural multipotentiality of the primary leptomeningeal cells.

[Contribution of immunohistochemistry and electron microscopy for the diagnosis of meningeal hemangiopericytomas. 15 case reports]

Meningeal hemangiopericytomas (HPC) are rare CNS tumors with a pour prognosis compared to meningiomas. In order to define diagnosis criteria, we performed an immunohistochemical and ultrastructural study in respectively 15 and 5 meningeal HPC. The following antibodies anti-KL1, EMA, vimentin, CD34, factor VIII, alpha-smooth actin, estrogen and progesteron receptors (RE, RP) were used in paraffin embedded sections whereas anti-NCAM and E-cadherin antibodies were used on frozen sections when available. We can differentiate meningeal HPC from meningioma because of a complete lack of immunostaining with epithelial markers as well as with NCAM antibody or RE and RP receptors. Besides a positivity with CD34 and alpha-smooth actin antibodies was always observed even focally in HPC. On the other hand, solitary fibrous tumor showed a strong and diffuse positivity with anti CD34 and anti-vimentin antibodies. Electron microscopy can be helpful in some instances showing membrane basal-like substance and absence of desmosomes.

Primary meningeal sarcomas with leiomyoblastic differentiation: a proposal for a new subtype of primary meningeal sarcomas

Two cases of primary meningeal sarcoma with leiomyoblastic differentiation are presented. In case no. 1, the tumor showed anaplastic spindle cell tumor components intermingled with anaplastic meningothelial components. Meningothelial tumor cells gradually became transformed into spindle tumor cells. Spindle tumor cells reacted with antisera to muscle actin (HHF-35) and alpha-smooth muscle actin. However, unchanged meningothelial tumor cells did not react with the antisera to HHF-35 and alpha-smooth muscle actin. Electron microscopy showed condensations of cytoplasmic fibers and pinocytotic vesicles in spindle tumor cells similar to those seen in smooth muscle cells. In case no. 2, the tumor cells consisted predominantly of sheets of round or polygonal cells as seen in an epithelioid leiomyosarcoma. The neoplastic cells had frequent nuclear inclusions, such as those seen in meningiomas. Immunohistochemically, the tumor cells reacted with antisera to desmin and to HHF-35. Electron microscopy showed a basal lamina around the cytoplasm of tumor cells. Intranuclear inclusions with various cytoplasmic organelles were frequently observed in the tumor cells, as in meningiomas. Interdigitating cytoplasmic processes and intercellular junctional complexes, however, were not found in the tumor cells. Two possible hypotheses explain the occurrence of leiomyoblastic characteristics of these cases. In case no. 1, leiomyoblastic cells originated from meningothelial cells with the advancement of meningothelial anaplasia. In case no. 2, pluripotential mesenchymal cells in the meninges differentiated into meningothelial and smooth-muscle cell lines at the time of tumor growth. With consideration of previous publications on primary meningeal sarcoma, these cases are the first reported primary meningeal sarcoma with leiomyoblastic and meningothelial differentiation.

[A case of primitive meningeal rhabdomyosarcoma. Histological, immunohistochemical and ultrastructural study]

A 64 year-old patient, complained of headache and neurological disorders. CT scan found a voluminous solitary tumor of the posterior part of the left cavernous sinus. Removal of tumor was followed by a rapid recurrence and by the patient's death. Histologic study found a malignant undifferentiated tumoral proliferation, with strap-like cells. Immunohistochemical stains were positive for conjunctival and muscular differentiation. Ultrastructural study revealed intracytoplasmic filamentous striated structure. The primary meningeal rhabdomyosarcoma is an exceptional tumor, generally affecting young patients. Its prognosis is poor and its histogenesis remains unclear.

Meningioma with granulofilamentous inclusions

The authors report a case of intracranial meningioma with granulofilamentous inclusions. A 50-year-old man had right trigeminal neuralgia due to trigeminal nerve compression by a petroclival tumor and received tumor resection. Microscopically, tumor cells containing eccentric nuclei and intracytoplasmic hyaline inclusions were arranged in sheets and whorls. The inclusions were negative for periodic acid-Schiff reaction. No histological anaplasia was seen. Immunohistochemistry showed epithelial membrane antigen reactivity on the cytoplasmic membrane. Immunoreactivity for vimentin was recognized in cytoplasm adjacent to inclusions. However, confocal laser microscopic study revealed immunoreactivity for vimentin even inside some inclusions. Ultrastructurally, interdigitation of cytoplasmic processes and desmosomes connecting adjacent cells were noted. Inclusions were composed of numerous fine osmiophilic granules attached by intermediates filaments. These findings were consistent with a meningioma with the granulofilamentous inclusions described earlier. The findings demonstrated by confocal laser microscopy and electron microscopy suggest that these granular materials may be the metabolic products of vimentin filaments.

Meningioma presenting as an intraoral mass in a patient with neurofibromatosis type 1

A 77-year-old woman with neurofibromatosis type 1 presented with ill-fitting dentures due to intraoral extension of a right temporal fossa mass. Computed tomographic scanning demonstrated that the masticator space mass bowed the zygomatic arch and remodeled the lateral orbit and maxillary sinus walls, findings that were consistent with the clinical diagnosis of a neurofibroma with possible malignant transformation. However, light microscopic, immunohistochemical, and ultrastructural examination of tissue from an incisional biopsy specimen were diagnostic of meningioma. This case illustrates that the clinicopathologic differential diagnosis of an enlarging mass in patient with neurofibromatosis should include sporadic, unrelated neoplasms as well as tumors known to be associated with the syndrome.

Malignant meningioma with rhabdoid transformation

We report a rare case of recurrent meningioma with malignant change and rhabdoid transformation in a 54-year-old woman who presented with severe headache and progressive weakness of the right extremities. The patient had a history of atypical meningioma and had undergone a craniotomy to remove a tumor nine years earlier. We discuss the distinctive morphologic, immunohistochemical staining and ultrastructural features of a recurrent malignant meningioma. A meningioma with rhabdoid transformation may indicate aggressive biologic and clinical behavior of the tumor.

[Lipomatous meningioma: report of two cases and review of the literature]

Lipomatous meningioma is a benign tumor characterized either by an admixture of mature adipocytes and meningioma or the production of triglycerides by neoplastic meningothelial cells assuming a lipoblast-like appearance. The authors report on two instances of this exceedingly rare lesion occurring in the left middle cranial fossa and over the right frontal convexity of two female patients aged 79 years and 60 years, respectively. In the former, the tumor was an incidental autopsy finding, while the latter underwent surgery for symptoms of intracranial space occupation. Light microscopy showed interwoven islands of fatty tissue and transitional meningioma in the first case; whereas a monomorphous signet-ring cell phenotype prevailed in the second. Oil-Red-O staining confirmed the presence of neutral fat in both specimens. Immunohistochemical coexpression of epithelial membrane antigen, vimentin, and S100 protein supported the meningothelial origin of tumor cells. On the other hand, the CD 68 macrophage antigen was not detected. Cytoplasmic lipid droplets along with hallmarks of meningothelial differentiation were visualized ultrastructurally in part of the meningioma component of the first case and throughout the second. These findings are consistent with a metaplastic origin of the adipocytic element. Whatever its histogenesis, lipomatous meningioma may, on occasion, represent a major challenge with therapeutic implications for both preoperative imaging and histological diagnosis.

[Rhabdoid meningioma: a potentially aggressive new variant]

Rhabdoid meningioma is a recently recognized clinicopathologic entity characterized histologically by cytoplasmic aggregates of intermediate filaments, and clinically by the propensity of such tumors to pursue an aggressive course. The authors report on clinical, radiologic and pathologic findings in three cases of rhabdoid meningioma identified in a retrospective surgical series of 204 meningothelial tumors. Patients included two females, aged 39 and 55 years, and a 54-year-old male. In the first two cases the tumors were located on the right and left lesser sphenoid wing, respectively; in the third case, the right cerebellopontine angle was affected. All three neoplasms evolved on a background on transitional meningioma and were conspicuous for dis-cohesive tumor cells and suppression of syncytical architecture. Immunohistochemistry and ultrastructural examination confirmed the meningothelial origin of inclusion-bearing rhabdoid cells. Although none of the tumors showed evidence of histologic anaplasia and Ki-67 labeling indices remained inferior to 2%, infiltrative growth into adjacent brain was noted in all three cases. On follow-up ranging from 8 months to 6 years, the patients remained either disease-free or alive with nonprogressive residual tumor. On account of their clinical behavior, well-differentiated rhabdoid meningiomas will be accommodated in the category of atypical meningiomas (WHO grade II). Their pathogenesis is likely to involve disrupted cytoskeletal integration of cell motility and proliferation, of which the rhabdoid phenotype may possibly represent a morphologic correlate.

Fibrous meningioma with tyrosine-rich crystals

A 58-year-old African-American woman presented with a 6-month history of headaches. A magnetic resonance imaging scan of the head revealed a 5-cm, enhancing dura-based mass in the left parietal region. The variably cellular tumor was composed of uniform spindle cells associated with intercellular collagen and numerous radially arranged "petal-shaped" clusters of eosinophilic crystals. The tumor was diagnosed by light microscopy as a fibrous meningioma. Ultrastructural examination disclosed cells with complex interdigitating processes connected by desmosome-like cell junctions, abundant intercellular collagen fibers, and prominent, densely osmiophilic crystals featuring radiating teardrop shaped petals emanating from a central core. A positive Millon reaction showed these crystals to consist at least in part of tyrosine. By morphology, histochemistry, and ultrastructure, the crystals resembled tyrosine-rich crystals occurring in salivary gland tumors. This is the first report of a fibrous meningioma containing tyrosine-rich crystals.

Clear cell meningioma of the lumbo-sacral spine with chordoid features

Clear cell meningioma (CCM) is a peculiar variant that differs from conventional meningioma in affecting younger patients, arising more often in spinal or cerebellopontine locations, and showing a higher recurrence rate. Classical meningothelial areas are scarce in these tumors and the differential diagnosis with other neoplasms, particularly metastatic carcinoma, is often difficult. We report a case of clear cell meningioma from the lumbosacral spine in which location, radiologic presentation, light microscopic appearance in initial sampling, and some of the ultrastructural findings were reminiscent of chordoma. The tumor cells were diffusely positive for vimentin and very focally positive for epithelial membrane antigen. Ultrastructural demonstration of interdigitating cell processes joined by numerous desmosomes confirmed the diagnosis of CCM.

Meningeal melanocytoma: a case report and literature review

The clinicopathologic, immunocytochemical, and electron microscopic features of a case of meningeal melanocytoma arising in the phylum terminale are reported. Meningeal melanocytoma is an uncommon tumor that must be distinguished from metastatic or primary malignant melanoma, meningeal melanocytic nevi, pigmented meningioma, pigmented schwannoma or neurofibroma, and pigmented primitive neuroectodermal tumor. This is a difficult differential diagnosis that can be best archived by complementing histological examination with a selected panel of antibodies and, most important, electron microscopic study. The distinctive ultrastructural appearance of most of these lesions point to this technique as the gold standard in pigmented proliferations of the nervous system.

Clear cell meningioma variant and clinical aggressiveness

The few reports about clear cell meningiomas (CCM) point to an inordinate clinical aggressiveness despite their histological benignity. We studied 5 CCM aiming to assess their clinicopathological, cytometric, and ultrastructural features. Two patients were females and 3 males, with a mean age of 36 years. Two tumors were spinal, one of the cerebral convexity, one of the tentorium-clinoid region, and one of the base of the skull. The first 3 were totally removed and have not recurred for a mean follow-up time of 40 months. The tentorium-clinoid and the skull base tumors had radical subtotal and partial resections, and recurred after 16 and 1.5 months, respectively. All tumors but one, a non-recurrent one, presented no signs of histological anaplasia. The proliferative capacity, as assessed by MIB-1 staining index (SI), of recurrent tumors was slightly higher than that of those tumors that did not recur. All cases showed DNA diploid pattern. Amianthoid-type fibers were disclosed on ultrastructural study. CCM arose in patients younger than those with other variants of meningioma, the spinal canal and the posterior fossa were the common sites. Finally, intracranial tumors were linked to an aggressive behavior.

Solitary fibrous tumor of the meninges

The clinical, radiologic, and pathologic features of a case of solitary fibrous tumor of the meninges at the base of the brain are reported. The tumor caused clinical symptoms in a 42-year-old Caucasian male which were indicative of compression of hypothalamus, basal ganglia, and third ventricle. Radiologically it was a large extra-axial mass isointense to brain parenchyma on precontrast T1-weighted images that filled the suprasellar cistern and deformed the left cerebral peduncle. At surgery, the tumor was firm to hard and attached to dura. Histologically the tumor was composed of spindle-cell proliferation in a collagen-rich background but exhibited regional variations. CD34 immunoreactivity was a prominent histologic finding. Ultrastructural features of meningioma, such as complex interdigitation of cell processes and intercellular specialized junctions were absent. The cells showed the typical appearances of fibroblasts with proximity of banded collagen and precollagen and cytoplasmic rough-surfaced endoplasmic reticulum. DNA ploidy analysis showed diploid DNA content. Awareness of this neoplasm may lead to increasingly frequent recognition and the current WHO classification of brain neoplasms should be modified to include this new entity.

Meningeal melanocytoma: case report and review of the literature

We report a case of meningeal melanocytoma in the thoracic spinal cord of a 44-year-old woman and review previously documented cases. Our patient experienced numbness and tingling in her left leg for 8 years, and low back pains with intermittent claudication for the previous 2 months. A histologically benign 20-mm tumour was totally resected. Radiation therapy was not given. The tumour showed the histological, immunohistochemical and ultrastructural features of a meningeal melanocytoma. The patient is alive without recurrence 4.5 years after surgery.

Establishment and characterization of cell lines derived from a transplantable rat malignant meningioma: morphological heterogeneity and production of nerve growth factor

A cell line (KMY-J) was established from a transplantable tumor (MM-KMY) derived from a spontaneous malignant meningioma arising in an aged F344 rat, and three cloned cell lines (KMY-1, KMY-2 and KMY-3) were induced from the parent KMY-J. Morphologically, KMY-J and tumors induced in syngeneic rats by KMY-J showed cell pleomorphism. All neoplastic cells in KMY-J and its tumors were immunoreactive to vimentin; occasional cells reacted to ED1 (rat macrophage/histiocyte-specific antibody) and alpha-smooth muscle actin (alpha-SMA), indicating expression of histiocytic or myofibroblastic immunophenotypes of meningioma cells. In contrast, KMY-1, KMY-2 and KMY-3 consisted of a uniform cell population differing from each other. KMY-1-induced tumors were similar histologically to meningeal fibrosarcomas. Dendritic cells seen in KMY-2 cultures gave an appearance of arachnoid trabecular cells. In KMY-3 and its tumors, large round cells and multinucleated giant cells were predominant. Cells of these cloned cell lines also reacted to vimentin, but were negative for ED1 and alpha-SMA. By the bioassay using PC12 cells and reverse transcription-polymerase chain reaction for nerve growth factor (NGF) mRNA, production of NGF was demonstrated in the parent and cloned cell lines. The present cell lines may prove useful for studying the histological features of meningeal tumors and the bioactive factors produced by meningeal cells.

Oncocytic meningioma

Six cases of meningioma showing oncocytic changes are described. The lesions were composed mostly of sheets, nests, and cords of large polygonal cells with finely granular eosinophilic cytoplasm rich in mitochondria. Neoplastic cells showed nuclear pleomorphism with prominent nucleoli. Necrosis and high mitotic rate were present in the majority of cases. Oncocytic differentiation was demonstrated by conventional histology, immunocytochemistry, electron microscopy, and Western-blot analysis. Oncocytic meningiomas showed an aggressive behavior; recurrences were observed in three cases, and invasion of brain cortex was evident in other two cases.

Solitary fibrous tumor of the spinal cord

We report a case of primary solitary fibrous tumor occurring in the intramedullary thoracic spinal cord in a 47-year-old man. The tumor predominately consisted of spindle cells separated by abundant collagen; a few areas of hemangiopericytomatous morphology were also present. The diagnosis was confirmed by immunohistochemistry and electron microscopy. The tumor was reactive to vimentin and CD34 but was negative for glial fibrillary acid protein (GFAP), S-100, smooth muscle actin, epithelial membrane antigen, HMB-45, myelin basic protein, and keratin; ultrastructural examination showed fairly undifferentiated cells within a collagenous matrix, few tight junctions, and sparse extravascular basement membrane. The occurrence of this tumor within the spinal cord parenchyma and in other extraserosal sites emphasizes the current belief that solitary fibrous tumors arise from mesenchymal tissues and are not restricted to the pleura and other serosal surfaces. Furthermore, solitary fibrous tumor is an entity that must be considered in the differential diagnosis of spindle cell central nervous system neoplasms.

Intracytoplasmic chromophobe inclusion bodies in an anaplastic meningioma

Intracytoplasmic inclusion bodies are rarely found in meningiomas. A 74-year-old woman had an anaplastic meningioma with intracytoplasmic chromophobe inclusion bodies (CIB) histologically. These CIB were various shapes, e.g. round, teardrop-like, fusiform, horse-shoe-like, crescentic and perinuclear. The size of CIB ranged from 7 to 14 microns and the nuclei of the tumor cells with CIB were often eccentric. Most CIB were immunopositive only for vimentin, staining more intensely than surrounding cytoplasm in a comparative study using adjacent sections stained with hematoxylin-eosin and vimentin. CIB showed loosely textured filamentous structures which were in parallel and entangled arrangements ultrastructurally. The diameter of the filaments was 13-14 nm and they were thicker than normal intermediate filaments. Moreover, these filaments appeared to be studded with granular and fuzzy substances. These findings suggest that CIB are mainly composed of abnormally synthesized and arranged vimentin filaments.

Prostaglandin D synthase (beta-trace) in human arachnoid and meningioma cells: roles as a cell marker or in cerebrospinal fluid absorption, tumorigenesis, and calcification process

Glutathione-independent prostaglandin D synthase (PGDS) is an enzyme responsible for biosynthesis of prostaglandin D2 in the CNS and is identical to a major cerebrospinal fluid protein, beta-trace. Although PGDS has been identified recently in rat leptomeninges, little information is available about human meninges or meningiomas. Here, we report PGDS to be expressed consistently in 10 human arachnoid and arachnoid villi and in 21 meningiomas by immunohistochemistry, Western blot, and reverse transcription (RT)-PCR analyses. In arachnoid, PGDS immunoreactivity was seen in arachnoid barrier cells but was negligible in arachnoid trabecula and pia mater. In contrast, in arachnoid villi, PGDS was seen in core arachnoid cells rather than in the cap cell cluster or arachnoid cell layer. Meningioma cells also showed intense immunoreactivity in the perinuclear region, and it was often concentrated within meningocytic whorls and around calcifying psammoma bodies. Immunoelectron microscopic data, when compared with the ultrastructure, showed that PGDS was localized at rough endoplasmatic reticulum of arachnoid and meningioma cells. Western blot showed a 29 kDa immunoreactive band indicating PGDS, but the extent of expression was variable from case to case, which was compatible with immunohistochemical data. RT-PCR revealed PGDS gene expression in all meningiomas studied, regardless of histological subtypes, and also in human arachnoid villi. Because human arachnoid and meningioma cells exclusively express PGDS, it can be considered their specific cell marker. These results show functional differences in various types of meningeal cells attributable to differences in PGDS expression.

Morphological and ultrastructural study of the histogenesis of meningeal granular cell tumors in rats

To clarify the cell of origin of granular cell tumors in the rat brain, light and/or electron microscopic examinations were performed on 40 cases of spontaneous meningeal tumors in Wistar (Jcl: Wistar) rats. The meningeal tumors were histologically subclassified into 3 types: meningothelial meningiomas (MMs), 3 cases; granular cell tumors (GCTs), 28 cases; and mixed forms (MIXs) of GCTs and MMs, 9 cases. Of these tumors, 2 MMs, 2 GCTs, and 3 MIXs were examined by transmission electron microscopy. Tumor cells of MMs were characterized by cytoplasmic intermediate filaments and prominent interdigitating cell processes often connected with cellular junctions without surrounding basal laminae. GCTs were composed of 2 cell types: granular cells with many dense bodies and filamentous cells with fine intermediate filaments. MIXs consisted of granular cells, filamentous cells, and intermediate cells. The tumor cells in GCTs and MIXs were apposed to each other and connected with cellular junctions. MIXs displayed a spectrum of cellular differentiation in that 2 MIXs had a close morphological resemblance to GCTs and the other one to MMs. These findings indicate there might be a histogenetic sequence among MMs, GCTs, and MIXs. The present study supports the suggestion that GCTs and MIXs may be variants of MMs from the meningeal arachnoid cell.

In vitro chemotherapy of steroid receptor positive human meningioma low-passage primary cultures with nitrosourea-methionine-steroid conjugates

The antiproliferative activity of two nitrosourea-methionine-steroid conjugates, N-[N'-(2-chloroethyl)-N'-nitrosocarbamoyl] (CNC)-L-methionine-testosterone-17-ester and CNC-L-methionine-dihydrotestosterone-17-ester, was investigated in two meningioma low-passage primary cultures that had been derived from human meningiomas and characterized with regard to proliferation pattern and progesterone receptor content. Treatment was given over 4 days. Cytotoxicity (concentrations investigated: 50, 100, and 200 microM) was compared with the effects of the equimolar mixtures of CNC-Met plus steroid. The steroid-linked nitrosoureas were superior to their unlinked components. CNC-Met itself displayed no or marginal activity, whereas the steroid component displayed significant activity.

Filamentous aggregates in a meningioma

The light microscopic and ultrastructural appearances of unusual filamentous aggregates in a right parietal meningioma in a 14-year-old boy are described. The tumor showed prominent meningothelial as well as fibroblastic components and was graded as an atypical meningioma. By light microscopy, eosinophilic, PAS-positive, granular, irregularly shaped Rosenthal fiber-like structures were widespread within the tumor, in both an intra- and an extracellular location. By immunohistochemical staining, similar location of positivity was obtained for vimentin, laminin, and collagen type IV. The inclusions were nonreactive for keratin, lysozyme, alpha-1-antitrypsin, and ubiquitin. Ultrastructurally, these aggregates were composed of an irregular tangle of filaments with electron dense condensations, sometimes with a lattice pattern. The intracellular aggregates were membrane-bound, and some were found within dilated rough endoplasmic reticulum, while extracellularly, they filled up spaces between adjacent tumor cells. Less prominently, flocculent osmiophilic nonfilamentous material was also seen within the inclusions. These observations suggest that these novel inclusions in a meningioma are composed of intermediate filaments (vimentin) and extracellular matrix proteins, with active synthesis in the rough endoplasmic reticulum and subsequent extrusion from the tumor cells into the extracellular spaces.

Considerations on the tendency for calcification in meningiomas

Calcifications in meningotheliomatous and fibromatous meningiomas were demonstrated after maceration under the scanning electron microscope and by pluck preparation. In five predominantly meningotheliomatous and five fibromatous meningiomas vascular features were studied after injection of Indian ink. The influx of calcium into the tumor parenchyma is thought to be related to long vessel loops and parallel coursing vessels which act as a countercurrent multiplication system similar to the loops of Henle in the kidney. Abruptly changing of diameter of vessels reduces the flow rate and enhances the transport of ions across vessels walls. Furthermore, the fine structure of endothelium favors the escape of ions into vessel walls and into parenchyma. Possible consequences of an intratumoral Ca overload are briefly discussed.

Clear cell meningioma: a case report

A case of clear cell meningioma in a 12-year-old male is reported. The tumor was located at the left side cerebellopontine angle, and characterized by sheets of patternless clear cells rich in cytoplasmic glycogen. Vague whorl formation and focal small clusters of typical meningothelial cells were the most important diagnostic features. The tumor cells showed positive immunoreactivity for vimentin, epithelial membrane antigen (EMA), and S100 protein. Cytokeratin and glial fibrillary acidic protein (GFAP) were negative. Ultrastructural features exhibited were abundant cytoplasmic glycogen particles, desmosome-like junctions and tangles of intermediate filaments, while cell membrane interdigitations were few. Clear cell meningioma is rare and is potentially aggressive in that it may recur, spread locally, and even metastasize, despite its bland histologic appearance. There is probably a predilection for younger age group. It is histologically unique but should be differentiated from other mimicking clear cell tumors of the central nervous system, including metastatic renal cell carcinoma, hemangioblastoma, oligodendroglioma, and clear cell ependymoma.

Leptomeningeal fibroma

Few cases of benign fibrous tumors have been reported in the central nervous system. Of the 9 cases in the literature only 1 was adjacent to the leptomeninges. We report a case of a fibroma of the leptomeninges of very low cellularity with calcified areas that had typical findings of a fibroma by electron microscopy. Immunophenotyping revealed unexpected positivity for S-100 and glial fibrillary acidic proteins. The histogenesis of this lesion may be a pluripotential cell, or the expression of these antigens may be induced by local factors in the central nervous system. The incidence of this unusual lesion is unknown, and ours is more typical of extracranial fibromas than the previously reported cases.