[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.