Concentric lamination of glial processes in oligodendrogliomas

Immunohistochemical and Ultrastructural Studies of Oligodendrogliomas Revealed Features of Neuronal Differentiation

In an attempt to characterize differentiation in oligodendrogliomas, 39 cases were examined immunohistochemically with 5 neuronal markers, synaptophysin, neuron- specific enolase, neurofilament proteins, protein gene product (PGP) 9.5, and micro tubule-associated protein 2 (MAP2), in addition to glial fibrillary acidic protein (GFAP). Positive immunolabeling was obtained for neuron-specific enolose in 29 cases (74%), synaptophysin in 21 cases (54%), PGP 9.5 in 33 cases (85%), and MAP2 in 23 cases (59%). All cases were negative for neurofilament, and 90% stained for GFAP. Eight cases were further studied ultrastructurally, and in five cases features of neuronal differentiation were identified in some of the typical neoplastic oligodendro cytes—small neuritic cellular processes with microtubules and focal synapse-like junc tions, as well as sparse neurosecretory granules. It was concluded that, both immuno histochemically and ultrastructurally, oligodendrogliomas may exhibit features of neuronal differentiation. These previously unreported features of oligodendrogliomas call into question conventional immunohistochemical and electron microscopic crite ria used in distinguishing oligodendrogliomas from tumors showing similar histologic appearance, especially central neurocytomas and dysembryoplastic neuroepithelial tu mors. Int J Surg Pathol 2(1):47-56 1994

The fine structure of ependymomas

Electron microscopy is a useful diagnostic technique in order to confirm or establish a definitive diagnosis in brain tumors that may have an atypical histological pattern, which requires a concrete diagnosis. In ependymomas, electron microscopy reveals morphological characters that have a pathognomonic diagnostic value, therefore allowing a definitive diagnosis. The main fine structural criteria of ependymomas consist of the numerous microvilli and cilia, which are incorporated in the cell body or extended freely in the intracellular space; the centriole or blepharoplast, which is located in the basis of the cilia; the large number of the fragmented microtubules in the perikaryon and the cellular processes (any small cellular projection into the neutrophil or intracellular space); the junctional apparatus between the cells, such as zonula adherens, zonula occludens and puncta adherentia; the basement membrane-like structure, seen in papillary ependymomas and ependymomas of the filum terminale; and the elongated cells in the loose intracellular space, commonly seen in myxopapillary ependymomas.

Molecular markers that identify human astrocytomas and oligodendrogliomas

The classification of human gliomas is currently based solely on neuropathological criteria. Prognostic and therapeutic parameters are dependent upon whether the tumors are deemed to be of astrocytic or oligodendroglial in origin. We sought to identify molecular reagents that might provide a more objective parameter to assist in the classification of these tumors. In order to identify mRNA transcripts for genes normally transcribed exclusively by oligodendrocytes. Northern blot analysis was carried out on RNA samples from 138 human gliomas. Transcripts encoding the myelin basic protein (MBP) were found in an equally high percentage of tumors that by neuropathological criteria were either astrocytic or oligodendroglial. In contrast, proteolipid protein (PLP) and cyclic nucleotide phosphodiesterase (CNP) mRNA molecules were found significantly more often in oligodendrogliomas than in astrocytomas. The strongest association with histological typing was found with the transcript for the myelin galactolipid biosynthetic enzyme UDP-galactose: ceramide galactosytransferase (CGT), which was about twice as frequently detected in tumors of oligodendroglial type. Results of glycolipid analyses were previously reported on a subset of the tumors studied herein. Statistical analyses of both molecular and biochemical data on this subset of astrocytomas, oligoastrocytomas, and oligodendrogliomas were performed to determine if a panel of markers could be used to separate astrocytic and oligodendroglial tumors. The presence of asialo GM1 (GA1) and the absence of paragloboside occurred most frequently in oligodendrogliomas. Ceramide monohexoside (CMH) levels correlated highly with the expression of mRNA for 4 myelin proteins: CGT, MBP, CNP, and PLP. The best combination of 2 markers of oligodendroglial tumors was CGT and GA1; the best combination of 3 markers was the presence of CGT, GA1, and the absence of paragloboside. We conclude that this combination of markers could be useful in distinguishing between astrocytic and oligodendroglial tumors.

FURTHER OBSERVATIONS ON THE STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM

Direct evidence has been presented to confirm the existence of a spiral in the myelin sheaths of the central nervous system. An account of some of the variations in structure of central myelin sheaths has been given and it has been shown that the radial component of myelin sheaths has the form of a series of rod-like thickenings of the intraperiod line. These thickenings extend along the intraperiod line in a direction parallel to the length of the axon. The relative position of the internal mesaxon and external tongue of cytoplasm has been determined in a number of transverse sections of sheaths from the optic nerves of adult mice, adult rats, and young rats. In about 75 per cent of the mature sheaths examined, these two structures were found within the same quadrant of the sheath, so that the cytoplasm of the external tongue process tends to lie directly outside that associated with the internal mesaxon. The frequency with which the internal mesaxon and external tongue lie within the same quadrant of the sheath increases both with the age of the animal and with the number of lamellae present within a sheath. The possible significance of these findings is discussed.

Central nervous system neoplasms: indications for electron microscopy

Diagnostic dilemmas of biopsy specimens in the central nervous system (CNS) tumors are often the result of multiple factors, including fixation artifact, biopsy size, lack of immunohistochemical techniques to distinguish cell types, and unawareness of rare entities. Correct diagnosis and confirmation of diagnosis of primary CNS neoplasms is imperative and may require electron microscopic examination. In some instances, use of electron microscopy may be the only approach for accurate recognition of an entity. Although diagnostic electron microscopy is expensive and cost cutting is encouraged in today's practice of medicine, cost must be weighed against the consequences of even 1 patient developing CNS treatment-related necrosis or a radiation-induced neoplasm secondary to misdiagnosis of a benign entity. This study reviews the ultrastructural differences of three groups of diagnostically difficult CNS lesions: clear cell neoplasms (ependymoma, oligodendroglioma, central neurocytoma), rare entities containing astrocytes invested by a basal lamina (pleomorphic xanthoastrocytoma, the desmoplastic neuroepithelial tumors of infancy), and benign entities characterized by transitional cell forms (subependymoma, subependymal giant cell astrocytoma).

Crystals in an oligodendroglioma: an optical, histochemical, and ultrastructural study

The report describes an oligodendroglioma that was examined in four biopsies and contained a large number of intracytoplasmic crystals. The crystals appeared in neoplastic cells with eosinophilic cytoplasms and eccentric nuclei. They were positive to periodic acid-Schiff stain and resistant to diastase. A lysosomal genesis of the crystals is proposed on the basis of a transition observed between lysosomal bodies with lipid droplets and those with crystalloid electron-dense structures. The morphologic and histochemical features of these crystals are compared to those in other tumors, lesions, and nonneoplastic cells.

Intraventricular neurocytoma: clinicopathological features of six cases

The clinical and pathological features of six patients with so-called "intraventricular oligodendroglioma" are reported. The tumor had no predilection for sex, and the patients' age at diagnosis ranged from 15 to 39 years. The lesions were located in the lateral and/or third ventricles. Total removal of the tumor was performed in three patients, and the remaining three underwent partial resection. Postoperative irradiation was given to five patients. A follow-up study revealed that five patients were free of recurrent tumor at 15 to 227 months after treatment, and one was alive with disease 25 months after surgery. Histologically, all tumors were composed of small uniform cells, with perinuclear halos and regular round nuclei. Tumor cells were sometimes arranged around nucleus-free fibrillary zones. Mitoses were infrequent. Ultrastructurally, neoplastic cells had round nuclei with dispersed heterochromatin and organelle-sparse cytoplasm containing occasional microtubules, 20 to 25 nm in diameter, and scattered dense-core vesicles, 100 to 200 nm in diameter. Cell processes containing dense-core and clear vesicles were frequently present. Thus, these neoplasms should be considered neuronal in origin, and should be classified as "intraventricular neurocytomas."

Astrocytic characteristics of oligodendroglioma. Fine structural and immunohistochemical studies of two cases

Two oligodendrogliomas were studied by light and electron microscopy. Additionally, an immunohistochemical study for glial fibrillary acidic protein (GFAP) was carried out. Some tumor cells exhibited glial filaments and perivascular end-feet, as on the one hand is characteristic of astrocytes, and glycogen granules and zonulae adherents which on the other hand are often seen in astrocytes but rarely in oligodendrocytes. Tumor cells with or without astrocytic characteristics showed the common fine structures and appeared to be on the same cell line. Our fine structural and immunohistochemical findings suggest that oligodendroglioma cells are of an astrocytic nature.

The fine structure of gliomatosis cerebri

The ultrastructural features of five biopsies of gliomatosis cerebri (GC) are described. Four main types of tumour cells are seen: anaplastic astrocytes poor in organelles with a variable amount of glial microfilaments; atypical oligodendrocytes with scanty cytoplasm in which microtubules are present; intermediate forms with aboundant cytoplasm rich in organelles, with microtubules and microfilaments; and small cells with round nuclei and a very scanty rim of cytoplasm. In two cases several concentrically folded cytoplasmic lamellae of glial processes were arranged either around themselves or around the perikaryon of other cells. This ultrastructural study indicates that GC is a neoplastic process of small undifferentiated elements, transitional forms of astroglia (to oligodendroglia) and anaplastic cells of astrocytic origin in all stages of development.

Ultrastructure of concentric laminations in primary human brain tumors

Ultrastructural concentric laminations have previously been thought to be specific to oligodendroglioma. However, these structures were also recognized in fibrillary astrocytomas, a mixed glioma and a glioblastoma. These laminations continued or closely related to attenuated processes or cytoplasm of astrocytic tumor cells. In addition, some lamellae contained glial filaments. It is considered that the concentric laminations are derived from attenuated astrocytic processes and have no relationship with myelin.

Pathology of acoustic nerve Schwannoma in vivo and in vitro

The ultrastructural pattern of the acoustic nerve Schwannoma was studied on surgically excised tumours and on explants cultured in vitro. The typical neoplastic cell is elongated, spindle-shaped, coated with basement membrane and numerous protruding cellular processes. Cells demonstrating numerous microfilaments are also seen, sometimes intermixed with the typical spindle-shaped cells. Fibroblasts are not uncommon; nor are cells with a round nucleus and rich in organelle cytoplasm, resembling endothelial cells. Numerous collagen fibres and "Luse bodies" are seen in the extracellular space, especially in areas of low cellularity. Round or ovoid cells partially coated with basement membrane are not uncommonly seen in various areas of the neoplasm. In culture, several cells demonstrate fibrillary cytoplasm and long thin cellular processes are frequently seen. Unusual features, such as enwrapping of the cytoplasmic processes forming laminated myelin-like figures are occasionally seen in the surgical specimens as well as in the in vitro cultured explants.

Crystals in a gastric schwannoma

A gastric schwannoma containing large numbers of intracytoplasmic crystals is described. The latter are compared with intracytoplasmic crystals found in the cells of other tumors and their nonneoplastic cell counterparts. The extreme morphologic and histochemical heterogeneity of the different types of crystals is emphasized.

The ultrastructure of oligodendrogliomas

Seven Oligodendrogliomas (2 with uniform cell type, 4 with cellular or tissue variability, and 1 with glioblastomatous changes) were examined ultrastructurally. The tumor cells were of two principal types with morphologic transitions between the two main types. The two principal cell types were identified as type 1 (undifferentiated) and type 2 (differentiated) on the basis of the number of anaplastic cells in an individual tumor and on the observations of Mori and Leblond (21) on non-neoplastic oligodendrocytes. Most of the tumor cells in all tumor exhibited similar histologic and ultrastructural characteristics including their arrangement and their tendency to form cytoplasmic processes which sometimes formed short stacks. These features were also recognizable in the glioblastomatous example and confirmed the presence of an oligodendroglial component. In addition to these characteristics, an increase in size and number of mitochondria, abundant intracytoplasmic structures, microtubules were regularly present in virtually all tumor cells. Cells rich in cytoplasmic filaments were present. These were identified as reactive astrocytes or as oligodendroglial tumor cells. Thus neither cytoplasmic filaments nor microtubules appear to be specific morphological markers for oligodendroglia or astrocytes; only the predominance of one of these structures permits cytogenetic identifications. The cytologic characteristics are not specific morphologic markers; however, recognition of their presence provides important diagnostic information.

Ultrastructure of oligodendrogliomas

The study of 18 oligodendrogliomas shows a number of characteristics which indicate a common hypothelial stem cell. The main cytologic characteristics are: a) high number of mitochondria, frequently atypical; b) polygonal crystalline structures in the cytoplasm in most of the tumors studied, and c) cytoplasmic microtubuli. None of these characteristics can be considered as pathognomic for the oligodendrogliomas. However, rows of folding cell processes represent a fundamental structural principle of all oligodendrogliomas and since they have not been found in any other brain tumor and may be regarded as an inherent and specific characteristic of the oligodendroglial group.

Isomorphous and anaplastic (polymorphous) oligodendroglioma

The problem of the astrocyte-like cells and giant cells in oligodendrogliomas is discussed, basing on morphological data of 22 tumours diagnosed as isomorphous, anaplastic and polymorphous type of oligodendroglioma. Multinucleated cells are characteristic features for polymorphous type of oligodendroglioma and the origin of multinucleated Langhans-like cells caused by a virus factor is proposed.

Normal and benzo(a)pyrene-transformed fetal mouse brain cells. II. Ultrastructural study

An ultrastructural study was performed on normal and Benzo(a)-pyrene(B(a)P)-transformed fetal mouse brain cells. Early subcultures of a strain initiated from whole brain presented three cell types in vitro: astroglial, poorly differentiated glial, and spongioblastic types. After B(a)P-treatment, there was an exclusive transformation and the growth of neuroglia sometimes without gliofibrillary maturation, but with the presence of glial fibrillary acidic protein (GFAP) in the cytoplasm. Early subcultures of another strain initiated from cortex only presented poorly differentiated neuroglial cells. After transformation, cell maturation as evidenced by gliofibrillogenesis and GFAP production by these cells was observed. In both cases, the potentiality of glial differentiation after in vitro malignant transformation by a chemical carcinogen seemed preserved.

Production of myelin by neoplastic cells

Formation of myelin sheaths by neoplastic cells was found in a spinal ganglioneuroma. All phases of initial myelination were observed including the formation of a mesaxonal spiral and the fusion of its lamellae into a major dense line. A unique aspect of neoplastic myelin formation was the formation of sheaths around bundles of extracellular fibrils rather than axons or cell processes. Formation of myelin sheaths around extracellular material has never been observed before. The findings have implications on the mechanisms controlling initial myelination.

[External temporal biopsy in a case of infiltrating limbic glioma: study of astrocytic membranous wrapping whorls (author's transl)]

An intracranial hypertension was found at autopsy to be due to a limbic infiltrating glioma. A cortical temporal biopsy had been done 14 months before, whose ultrastructural results are reported. Membranous whorls, made of two dense membranes with a variable separative space are seen around neurones, dendrites, axons, synapses and oligoglial cells; they derived from astrocytes and are joined by 2 types of cell junctions: gap-junctions and puncta adherentia. Relations between reactive and tumoral gliosis are discussed.

II. Ultrastructural changes in focal retinal ischaemia

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ELECTRON MICROSCOPIC OBSERVATIONS ON ASTROCYTOMAS

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