Neural differentiation in the OTT-6050 mouse teratoma. Production of a tumor fraction showing melanogenesis in neuroepithelial cells after centrifugal elutriation

Melanosomal melanin pigment in pleomorphic xanthoastrocytoma, evidence for neuronal-glial origin: A case report with review of the literature

We describe a unique case of pleomorphic xanthoastrocytoma (PXA) in a 19-year-old male presenting with the chief complaint of seizures. On radiology, the tumor was located in the temporal lobe. It was cortically based and solid cystic in nature. Light microscopy showed pleomorphic large polygonal cells with inclusions, nuclear clustering, lipidization, and foamy cytoplasm intermingled with spindle cells arranged in sweeping pattern and focally containing cytoplasmic brownish black pigment. The pigment stained black with Fontana-Masson stain and bleached with potassium permanganate. Gomori silver stain showed reticulin fibers surrounding individual tumor cells as well as groups of cells. On immunohistochemistry, tumor cells were positive for GFAP, S-100 and focally for synaptophysin and CD34 but negative for HMB-45. CD34 revealed a specific membranous pattern around individual cells as well as groups of cells along the fibers replicating a reticulin pattern. The ultrastructural examination showed supporting melanosomes, thus confirming the melanin pigment. Sequencing for BRAF V600E showed a heterozygous mutation. To our knowledge only five cases of PXA with melanin pigment have been reported and none of which described BRAF V600E mutation analysis. This case provides further insight into the origin and pathogenesis of pigmented astrocytic tumor, additionally highlighting the characteristic CD34 staining pattern.

Pigmented pleomorphic xanthoastrocytoma: a rare variant and literature review

A 16-year-old male teenager presented with seizure and loss of consciousness for 20 min. Magnetic resonance imaging demonstrated a mass occupying the right medial temporal lobe. Histological examination revealed a non-pigmented area with spindle-shaped and large xanthomatous pleomorphic cells and a pigmented region with pigmented neoplastic cells with fascicular arrangement. Immunohistochemical studies showed the tumor was positive for GFAP and low index of Ki-67. Considering the patient's history, clinical data and pathological findings, we rendered a rare variant named pigmented pleomorphic xanthoastrocytoma.

Lucien J. Rubinstein: enduring contributions to neuro-oncology

Dr. Lucien Rubinstein is best remembered for his significant contributions to the field of neuropathology, particularly in the classification of nervous system tumors. His accomplishments in basic neuro-oncology and in the formulation of diagnostic principles reflected a unique talent for synthesizing fundamental clinicopathological concepts based on skillful diagnostic investigation and a thorough understanding of neurobiology. Dr. Rubinstein was the leader in the establishment of cell cultures from central nervous system (CNS) tumors. He meticulously analyzed both light and electron microscopic features of CNS tumors, recorded his findings, and patiently drew sketches to be shared generously with his colleagues and students. As a pioneer in neuropathology, in his work Dr. Rubinstein set the foundation for many enduring concepts in neurosurgery, neuro-oncology, neurology, and basic tumor biology.

Pigmented astrocytoma with suprasellar location: case report and literature review

A large suprasellar, partly cystic, contrast-enhancing tumor was resected from a 19-year-old woman who presented with bitemporal visual field defects and reduced visual acuity. Grossly, the tumor was brown and located in the subarachnoid space. Histologically, it was composed of spindle and pleomorphic cells, including giant tumor cells, with markedly pleomorphic nuclei. Reticulin fibers surrounded single cells and small groups of cells. Very few mitotic figures were found in the tumor, and no necrosis or microvascular proliferation was seen. The tumor thereby resembled a pleomorphic xanthoastrocytoma. Many of the tumor cells contained a dark-brown intracytoplasmic pigment, shown to be melanosomal melanin by ultrastructural examination. Immunohistochemical examination demonstrated that the pigment was present in glial tumor cells. Only four cases of pigmented astrocytic tumors have been published, none of these were suprasellar. Our patient received fractionated radiotherapy with a total dose of 48.6 Gy 14 months after gross total removal of the tumor. She is alive without relapse after 12-year follow-up.

Pigmented pleomorphic xanthoastrocytoma: report of a rare case with review of the literature

We describe a rare case of melanotic pleomorphic xanthoastrocytoma in a 32-year-old man who presented with partial complex seizures. Radiologically, the mass was located in the medial temporal lobe and was solid and cystic. Microscopic examination revealed features of a pleomorphic xanthoastrocytoma with some heavily pigmented cells. The pigment was demonstrated to be melanosomal melanin, which was confirmed by special stains, immunohistochemistry, and electron microscopy.

Tyrosinase is a new marker for cell populations in the mouse neural tube

Tyrosinase, the key enzyme in melanin synthesis, is expressed in pigment cells derived from both neural crest and neuroectoderm. The present study was performed to detect tyrosinase promoter activity and tyrosinase gene expression during murine brain development. Mouse tyrosinase 5' region (6.1 Kb) was used to direct lacZ expression in transgenic mice. During embryogenesis, the transgene reproduced tyrosinase expression in pigment cells but was also observed in embryonic neuroectoderm and migrating neural crest cells. Both tyrosinase and lacZ were detected in cell populations often organized in columnar arrangements and found throughout the entire neural tube, in the cranial region as well as in the spinal chord. In the developing brain, the highest density of positive cells was localized to ventricular and subventricular zones and to evaginations of the neural tube such as optic vesicle, pineal gland, and olfactory bulbs. These results demonstrate that tyrosinase promoter activity and tyrosinase expression are not restricted to differentiated pigment cells. We suggest that tyrosinase is a new marker for cell populations in the neural tube, and that expression is correlated to regions undergoing rapid cell proliferation.

Pigmented intracerebral neuroepithelial cyst: report of a case

A 35-year-old man with seizure disorder was found to have a parietal lobe neuroepithelial cyst. The lining of the cyst was made up of ependymal cells containing neuromelanin, which was confirmed ultrastructurally. This appears to be the first report of a pigmented neuroepithelial cyst in the brain parenchyma.

Melanotic cerebral ganglioglioma: evidence for melanogenesis in neoplastic astrocytes

A composite melanotic glial-ganglionic tumor was resected from a 17-year-old girl who presented with a 5-year history of epilepsy. Grossly, the tumor was partly cystic, partly solid, located superficially in the temporal lobe. Histologically, its glial component was composed of spindle and pleomorphic cells, including tumor giant cells, which were associated with Rosenthal fibers, eosinophilic granular bodies and marked desmoplasia. The cells had immunohistochemical and ultrastructural features of astrocytes, and some were invested by incomplete basal lamina. Thus, the tumor had many features in common with pleomorphic xanthoastrocytoma. However, its most striking feature was the presence of melanin pigment in numerous neoplastic cells. Immunoelectron microscopy revealed glial fibrillary acidic protein-positive intermediate filaments in tumor cells bearing melanosomes and premelanosome, proving their astrocytic nature. This case demonstrates, for the first time, melanosomal melanogenesis in human cells with astrocytic phenotype, and provides additional evidence for the ability of central neuroepithelial cell derivatives to produce melanin.

An immunohistochemical characterization of the primitive and maturing neuroepithelial components in the OTT-6050 transplantable mouse teratoma

The neuroepithelial component of the OTT-6050 mouse teratoma has previously been characterized as an experimental system for the study of differentiation and cytologic maturation in embryonal tumours of the human central nervous system. A number of transplantable tumours composed of primitive stem cells and of a neuroepithelial component displaying a spectrum of differentiation were previously produced by centrifugal elutriation of the dissociated OTT-6050 teratoma. These tumours have provided a reproducible cell population that has permitted the study of both the early and later stages of neoplastic neurocytogenesis. The purpose of the present study was to detect, by immunohistochemistry, the earliest stages of neurocytogenesis in these tumours as shown by the expression of neuron-associated microtubule proteins. This was correlated to the appearance and localization of other markers associated with neuronal and glial differentiation. The primitive neuroepithelial structures resembling neural tubes (medulloepithelial rosettes) contained single or small groups of cells which reacted with the monoclonal antibody TUJ1, specific for the neuron-associated class III beta-tubulin isotype. Immature neuroblasts and maturing polar neurons also showed immunoreactivity with TUJ1, whereas reactivity for microtubule-associated protein 2 (MAP2), tau, the 200 kilodalton isoform of neurofilament protein, neuron-specific enolase and synaptophysin was primarily seen in maturing neurons. By comparison, both medulloepithelial and ependymoblastic rosettes, neuroblasts and glial cells were immunopositive with monoclonal antibody TU27, which defines an antigenic site shared by most mammalian beta-tubulin isotypes. Astroglia were reactive with antisera to glial fibrillary acidic and S-100 proteins, but not with monoclonal antibody (MAb) TUJ1, or with MAbs to the other neuron-associated cytoskeletal proteins, MAP2, tau and the 200 kilodalton subunit of neurofilament protein. Our findings suggest that (1) expression of the class III beta-tubulin isotype is an early event during neoplastic neurocytogenesis, (2) this isotype is subsequently preserved in maturing neuronal populations, and (3) it is not present at detectable levels in stem cells or glial cells. The observation that morphologically undifferentiated neuroepithelial cells express a neuron-associated beta-tubulin isotype signifies the value of examining tubulin isotype expression in the characterization of normal and neoplastic neuroepithelial differentiation.

Microglial and neural differentiation in human teratomas

Ten human teratomas arising outside the central nervous system (CNS) were studied using a panel of immunohistochemical, and lectin histochemical stains to determine the relationship of the presence of microglia to markers of neural maturity or differentiation. Microglia, identified by silver carbonate, Ricinus communis agglutinin-1 (RCA-1), or both were found in eight out of ten cases. They were common in mature areas which also had S-100, glial fibrillary acidic protein, vimentin, neurofilament, and synaptophysin immunostaining. Microglia were distinguished from macrophages in necrotic foci. Cells which were RCA-1 positive and silver carbonate positive were found in immature neural tissues but these lacked all typical features of microglia. These observations indicate that true microglia are frequent in nonCNS teratomas and that they are found in association with other indicators of neural maturation. The presence of possible precursors in immature areas suggests that microglia undergo maturation concurrent with neural differentiation in these tumors.

Maturation of cerebellar neuroblastoma into ganglioneuroma with melanosis. A histologic, immunocytochemical, and ultrastructural study

A ganglioneuroma with areas of melanosis was resected from the cerebellum of a 6.5-year-old girl. At 2.5 years of age, she was diagnosed to have cerebellar neuroblastoma, which was incompletely resected and then radiated. Histologic, ultrastructural, and immunocytochemical studies undertaken on tissue from both stages of the tumor demonstrated a neuroblastic origin and differentiation into a predominantly neuronal tumor with limited astroglial participation. In addition, widespread deposition of basal lamina material, perineuronal distribution of S-100 protein-bearing cells and melanosis were found. The various features and unusual biology of the tumor are discussed in the light of a review of the literature.

Medullomyoblastoma. A histologic, immunohistochemical, and ultrastructural study

The light and electron microscopic features of a medullomyoblastoma arising in the cerebellar vermis of a 3-year-old boy are described. Differentiation along both glial and neuronal lines was present in the medulloblastoma component of the tumor. Astrocytic differentiation was confirmed by the observation of compact bundles of 8 to 10 nm glial filaments in cellular processes on ultrastructural examination, and by positive immunostaining for glial fibrillary acidic protein (GFAP). Neuroblastic differentiation was suggested by the demonstration of axon-like processes on silver impregnation, and ultrastructurally by the observation of microtubules, dense-core and clear vesicles, and rare synapse-like structures within cytoplasmic processes. The presence of both primitive and well-differentiated striated muscle fibers in the tumor was confirmed by the demonstration of thick and thin myofilaments and Z bands on electron microscopy, and by positive immunostaining for myoglobin. These findings clearly establish the presence of both neuroectodermal and rhabdomyoblastic components in this neoplasm, and thus set it apart from the pure rhabdomyosarcomas, which may also occur in the cerebellar vermis in children. This case also illustrates the usefulness of electron microscopy and immunohistochemistry in the diagnosis and histogenetic evaluation of primitive or poorly differentiated small cell tumors of the central nervous system.

Pigmented olfactory neuroblastoma: a new example of melanotic neuroepithelial neoplasm

The light and electron microscopic features of a pigmented olfactory neuroblastoma are described. The neuroblastic nature of the tumor was confirmed by the demonstration of axons, some of which originated from the neoplastic cells, and by the presence of dense-core vesicles in the perikarya and processes of the tumor cells. The tumor contained a large amount of pigment, most of which had the histochemical reactions of melanin, but some of which had that of lipofuscin. Electron microscopy failed to demonstrate the presence of melanosomes or premelanosomes: the pigment showed some of the features of neuromelanin, although the fine structural appearances were not typical. The pigment was interpreted in this case as presumably representing a modified catecholamine degradation product, perhaps related to lipofuscin. The presence of melanotic pigment in an example of olfactory neuroblastoma, unreported until now, augments the list of neurogenic neoplasms in which an association with melanin formation has been described. The significance of this association in tumors originating from the nervous system or its coverings needs further investigation, as the nature of pigment appears to be heterogeneous. These tumors may contain either melanosomal pigment or pigment identified as neuromelanin (or a related substance), seemingly regardless of the derivation of the pigment-bearing cells.

Neural differentiation in the OTT-6050 mouse teratoma. Production of a tumor fraction restricted to stem cells and neural cells after centrifugal elutriation

Dissociation and centrifugal elutriation procedures were applied to subcutaneous transplants of the OTT-6050 mouse teratoma line in order to enrich the neuroepithelial cells. One of the resultant cell fractions, designated IB-21, was then implanted beneath the renal capsule of syngeneic mice and rebanked every 3 to 6 weeks for a total of 58 passages over 5 years. Sequential passages resulted in a tumor restricted to stem cells and neural cells (neuroblasts and glial cells). The primitive neural cells lost the ability to form rosettes after the early transplants. Subcutaneous or intracerebral transplantation of these tumors evinced their capacity for further neuroepithelial differentiation, with the demonstration of astrocytes and occasional mature synapse-forming neurons. Conversion of the tumor to the ascitic form resulted in unorganized clusters of neoplastic cells in contrast to the highly structured embryoid bodies that are characteristic of the parent Ott-6050 line. The absence of non-neural cells in the IB-21 tumor fraction and its ability to demonstrate divergent neural differentiation suggest that a transplantable neural-determined cell population exists in the OTT-6050 mouse teratoma.