Granulofilamentous inclusions in a meningioma

Pathology and molecular genetics of meningioma: recent advances

Meningiomas are the most common intracranial primary neoplasm in adults. Although the spectrum of clinical and molecular genetic issues regarding meningiomas remains undefined, novel genetic alterations that are associated with tumor morphology, malignancy, or location have recently been discovered. This review focuses on recent advances in understanding of the heterogenous pathology of meningiomas, particularly on associations between the clinical, histological, etiological, epidemiological, and molecular genetical aspects of the neoplasm.

Granulofilamentous meningioma

A 55-year old female was referred to the Department of Neurosurgery, Kitasato Hospital, because of a hearing impairment. Neuroimaging revealed a typical meningioma attached to the falx in the right frontal region. During surgery, an encapsulated, circumscribed, reddish-gray, slightly hard tumor attached to the falx was completely removed by an interhemispheric approach. On light microscopy, many of the tumor cells contained eosinophilic inclusions with single or multiple vacuoles that displaced the cytoplasm. The nuclei of the tumor cells were eccentric. There were no signs of malignancy in the specimen. Electron microscopy revealed that most of the eosinophilic inclusions were composed of filaments measuring 12 nm in diameter. There have been several reports of benign meningiomas with eosinophilic inclusions composed of intermediate filaments. The microscopic differences between these types of tumor and rhabdoid meningiomas are very subtle, and it is important the two types of tumors are not confused. Benign meningiomas with eosinophilic inclusions comprising intermediate filaments, for example the tumor described in this report, have been diagnosed as granulofilamentous meningiomas, which is a subtype of benign meningioma.

Rhabdoid papillary meningioma

We have studied an uncommon case of rhabdoid papillary meningioma in a 15-year-old boy with a dura-based mass arising in the left posterior fossa. The patient exhibited prominent extracranial extension during the past 6 years, consisting of a mixture of both perivascular pseudopapillary growth and rhabdoid cytologic features of neoplastic meningothelial cells. The meningothelial features were evidenced by the focal whorl formation of tumor cells, coexpression of epithelial membrane antigen and vimentin, and ultrastructural findings of interdigitated cytoplasmic process and intercellular junction. However, the regional and histologic resemblances to ependymoma were further complicated by unexpected focal expression of glial fibrillary acidic protein, neurofilament, and alpha-smooth muscle actin of the tumor cells. The rhabdoid morphology was characterized by sheets of tumor cells with eccentric nuclei and abundant eosinophilic cytoplasm with often recognizable intracytoplasmic hyaline inclusions. These inclusions revealed ultrastructural paranuclear whorls of intermediate filaments, ruling out the other forms of intracytoplasmic eosinophilic inclusions resembling rhabdoid morphology. Diagnosis of an unusual rhabdoid papillary meningioma with aggressive behavior is resoluble by immunohistochemical and ultrastructural analyses.

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.

Primary cutaneous meningioma on the scalp: report of two siblings

Primary cutaneous meningioma (PCM) is a rare tumor whose pathogenesis is quite obscure. We reported PCMs occurring on almost the same occipital region of two siblings studied by histology, immunohistochemistry, and electron microscopy. Both lesions were attached to duras, but extracranial. One lesion was histologically diagnosed as meningothelial meningioma; its tumor cells showed electron microscopically interdigitating cytoplasmic processes with junctional complexes. The other was interpreted as fibroblastic meningioma; its tumor cells were arranged linearly in a stepping-stone arrangement and had small dense bodies in the cytoplasm. The tumor cells stained positively with anti-vimentin antibody. Both lesions had adenomatous hyperplasia of the eccrine glands. Although the histologic and electron microscopic features of these two lesions slightly differed from each other, their pathogenesis was essentially considered to be acoelic or rudimentary meningocele.

Nasal glioma: an immunohistochemical and ultrastructural study

A case of a 14 month old Japanese female infant presenting with nasal glioma is reported. The tumor had been noticed at the nasal radix since birth and had slowly and progressively enlarged. There was no communication between the tumor and the cranial cavity on radiological examination. The tumor was macroscopically anchored to the nasal septum by a fibrous stalk, and histologically consisted of nests or trabeculae of either polygonal or spindle cells with plump eosinophilic cytoplasm and oval nuclei, separated by vascular-rich connective tissue intermingled with multinucleated giant cells. These tumor cells were immunohistochemically positive for glial fibrillary acidic protein as well as for S-100 protein and vimentin. An electron microscopic examination revealed collagen fibers and basal lamina between the tumor cells and the fibroblasts. Tumor cells possessed abundant intermediate filaments, which showed occasional Rosenthal fiber-like structures, in their cytoplasm and processes. A few oligodendrocytes and cilia of 9 microtubule doublets either with or without 2 central microtubules were also noted. These clinicopathological findings suggested that this tumor was once an encephalo(meningo)cele, which probably degenerated as a result of the loss of intracranial communication and then appeared to be isolated from the intracranial tissue.

Novel eosinophilic intracytoplasmic inclusions in a meningioma

BACKGROUND

Two forms of inclusion, extracellular and intracytoplasmic, have been reported in meningiomas. The authors recently encountered a case of meningothelial meningioma with unusual round eosinophilic intracytoplasmic inclusions.

METHODS

Ultrastructural and immunohistochemical studies were performed on the surgically removed tissue.

RESULTS

Ultrastructurally, the inclusions were found in the cytoplasm and processes of the tumor cells. Each inclusion consisted of a dense central mass of filaments with a looser, less dense periphery of radiating filaments. At the periphery, crystalloid lamellar structures and granules were intermingled frequently. No limiting membrane was observed. Immunohistochemically, the inclusions were unreactive for five classes of intermediate filaments, actin, ubiquitin, and amyloid.

CONCLUSION

The intracytoplasmic inclusions were ultrastructurally distinct from those reported previously. The molecular aspect of these novel eosinophilic intracytoplasmic inclusions remained uncertain.

Rosenthal fibers producing a granular cell appearance in a glioblastoma

In this report we describe a glioblastoma multiforme with focal granular cell change. In most astroglial tumors with granular cells, the granular appearance is due to the presence of periodic acid-Schiff-positive, membrane-bound cellular debris. In the present case the granular appearance was due to the presence of many small Rosenthal fibers, which were immunoreactive for glial fibrillary acidic protein, vimentin, ubiquitin, and heat-shock protein 27, but not for alpha-B crystallin. The ultrastructural characteristics are described. These findings demonstrate that granulofilamentous inclusions with the appearance of Rosenthal fibers in glial tumors are a structurally heterogeneous feature.

Small heat-shock protein is expressed in meningiomas and in granulofilamentous inclusion bodies

FF cellular expression of estrogen receptor-related small heat-shock protein (HSP27) in meningiomas was investigated immunologically. A cytoplasmic distribution of HSP27 was demonstrated in surgical specimens of 22 of 26 cases with meningiomas and cultured meningioma cells derived from two individuals. By Western blotting, HSP27 was detected in every tissue homogenate of 17 cases studied. Thus, HSP27 appears to be constitutively expressed in most meningiomas. In anaplastic portions of one papillary meningioma, there were numerous granulofilamentous inclusion bodies [Goldman JE et al. (1980) Cancer 46:156-161]. The inclusion bodies were immunopositive for HSP27 despite the negativity of the tumor cytoplasms. Thus, HSP27 seems to participate in the formation of certain inclusion bodies in meningioma cells, like alpha B-crystallin which participates in the formation of Rosenthal fibers in astrocytes.

Cytokeratin filaments and desmosomes in the epithelioid cells of the perineurial and arachnoidal sheaths of some vertebrate species

Using electron microscopy and immunohistochemistry with a large panel of antibodies to various cytoskeletal proteins we have noted that the single- or multi-layered sheaths of epithelioid cells ("neurothelia") surrounding peripheral nerves (perineurial cells) or structures of the central nervous system, including the optic nerve (arachnoid cells), show remarkable interspecies differences in their cytoskeletal complements. In two anuran amphibia examined (Xenopus laevis, Rana ridibunda), the cells of both forms of neurothelia, i.e., perineurial and arachnoid, are interconnected by true desmosomes and are rich intermediate-sized filaments (IFs) of the cytokeratin type. Among higher vertebrates, a similar situation is found in the bovine and chicken nervous systems, in which the arachnoid cells of the meninges contain desmosomes and IFs of both the cytokeratin (apparently with restricted epitope accessibilities in the chicken) and the vimentin type, whereas the perineurial cells of many nerves contain cytokeratin IFs, often together with vimentin, but no desmosomes. In contrast, in rat arachnoidal and perineurial cells significant reactions have been observed neither for cytokeratins nor for desmosomes. In the human nervous system, cytokeratins and desmosomes have also not been seen in the various perineuria studied whereas desmosomes are frequent in arachnoidal cell layers which are dominated by vimentin IFs and only in certain small regions of the brain contain some additional cytokeratins. The occurrence of cytokeratins in the tissues found positive by immunohistochemistry has been confirmed by gel electrophoresis of cytoskeletal proteins, followed by immunoblotting. Our results emphasize both similarities and differences between the neurothelia on the one hand and epithelia or endothelia on the other, justifying classification as a separate kind of tissue, i.e., neurothelium. The observations of interspecies differences lead to the challenging conclusion that neither desmosomes nor cytokeratins are essential for the basic functions of neurothelial sheaths nor does the specific type of IF protein expressed in these cells appear to matter in this respect. The results are also discussed in relation to the cytoskeletal characteristics of other epithelioid tissues and of human neurothelium-derived tumors.

Bronchial carcinoid with paranuclear fibrillary inclusions related to cytokeratins and vimentin

A bronchial carcinoid with globular intracytoplasmic inclusions is reported. The inclusions stain brown with Grimelius silver impregnation and some show distinct immunoreactivity for chromogranin A. Tumour cells stain positively with antisera to neuron specific enolase, chromogranin A and not with antisera against ACTH, somatostatin or S-100 protein. The cells show distinct immunoreactivity for cytokeratins and vimentin, which is particularly intense in the intracytoplasmic inclusions. Desmin and glial fibrillary acidic protein are absent. Ultrastructural analysis reveals that the inclusions are composed of aggregates of filaments of 8-10 nm of diameter, intrapping a few neurosecretory granules. Immunohistochemical and ultrastructural data support the hypothesis that the inclusions are composed of intermediate filaments, whose metabolism and synthesis have somehow been deranged.

Microfilamentous carcinoid of the thymus: correlation of ultrastructural study with Grimelius stain

We observed a carcinoid of the thymus that was remarkable for the presence of intracytoplasmic inclusions-readily visible by light microscopy-in the majority of tumor cells. The inclusions were best seen in Grimelius-stained preparations, which also revealed argyrophilic granules present within or close to the masses. On electron microscope examination the inclusions were found to be composed of aggregates of filaments, probably of the intermediate type, which were at times accompanied by neurosecretory granules. The observed incompatibility between the presence of such inclusions and a homogeneous distribution of secretory granules in the cytoplasm is suggestive of a dysfunction of intracellular movements. Microfilamentous carcinoids may represent a class of tumor having a pathologic excretory process.