Rosette-forming glioneuronal tumor of the fourth ventricle. Two cases report and literature review. / Tumor glioneuronal formador de rosetas del IV ventrículo. Presentación de 2casos y revisión de la literatura.

Rosette-forming glioneuronal tumor of the fourth ventricle is a primary central nervous system tumor introduced in the group of glioneuronal tumors in the WHO classification of 2007. Initially it was described around the fourth ventricle, but recently have been published cases in different locations. We present 2cases of this rare tumor, both surgically treated. The first in a 41 year old man with typical symptoms of posterior fossa injury. The second in an 18 year old woman, with incidental finding of posterior fossa injury that was also surgically treated. We present pre- and post-surgical magnetic resonance images, histological pictures of this tumor and we make a review of the literature.

Medulloblastoma demonstrating multipotent differentiation: case report.

We report a 6-year-old boy who presented with a medulloblastoma demonstrating classic, myoblastic, neuronal, glial, and melanotic differentiation and manifesting as severe morning headache. Magnetic resonance imaging revealed a mass lesion with cystic components in the cerebellar vermis. He underwent suboccipital craniotomy and total resection of the tumor. The specimen consisted of three morphologically distinct components. The first component consisted of densely packed cells with round-to-oval highly hyperchromatic nuclei surrounded by scanty cytoplasm. Immunohistochemical staining revealed diffuse expression of neurofilament protein and focal expression of desmin and myoglobin. The second component consisted of long spindle-shaped cells with elongated nuclei and eosinophilic cytoplasm. Immunohistochemical staining revealed diffuse expression of neurofilament protein, desmin, and myoglobin. The third component consisted of cells with small, densely hyperchromatic nuclei and scanty cytoplasm in a fine fibrillary background. Mature ganglion cells and melanotic tumor cells were also observed. Immunohistochemical staining revealed diffuse expression of synaptophysin and neurofilament protein, and focal expression of glial fibrillary acidic protein, S-100 protein, desmin, and myoglobin. The diagnosis was medulloblastoma with myoblastic, neuronal, astrocytic, and melanotic differentiation. Medulloblastoma demonstrating multipotent differentiation is rare, but the features observed in this case support the idea that medulloblastoma originates from multipotent stem cells.

Highly cystic brain tumor: rare histological features in an ependymoma.

Ependymoma is a slowly growing tumor appearing mostly in children and young adults. Several histological patterns are described. We report a case with unusual microscopic features, composed mostly of multiple cysts. Ultrastructural and immunohistochemical examination confirmed the diagnosis. Neuropathologists should be aware of this particular change which can generate some diagnostic difficulties.

Woman aged 24 years with fourth ventricular mass.

April 2005. A woman aged 24 years presented with symptoms related to a tumor in the fourth ventricle. Cytologically, the tumor was biphasic with areas typical of a classic ependymoma, including rosettes, and other areas containing grossly atypical giant cells. Many tumor cells were GFAP-positive and ultrastructural examination revealed microvilli and cilia. The histopathologic abnormalities place this tumor among the ependymomas. Its focal giant cell phenotype is very rare, but has been reported in 4 intracranial or filum ependymomas.

Cellular mechanisms involved in the stenosis and obliteration of the cerebral aqueduct of hyh mutant mice developing congenital hydrocephalus.

Two phases may be recognized in the development of congenital hydrocephalus in the hyh mutant mouse. During embryonic life the detachment of the ventral ependyma is followed by a moderate hydrocephalus. During the first postnatal week the cerebral aqueduct becomes obliterated and a severe hydrocephalus develops. The aim of the present investigation was to elucidate the cellular phenomena occurring at the site of aqueduct obliteration and the probable participation of the subcommissural organ in this process. Electron microscopy, immunocytochemistry, and lectin histochemistry were used to investigate the aqueduct of normal and hydrocephalic hyh mice from embryonic day 14 (E-14) to postnatal day 7 (PN-7). In the normal hyh mouse, the aqueduct is an irregularly shaped cavity with 3 distinct regions (rostral, middle, and caudal) lined by various types of ependyma. In the hydrocephalic mouse, these 3 regions behave differently; the rostral end becomes stenosed, the middle third dilates, and the caudal end obliterates. The findings indicate that the following sequence of events lead to hydrocephalus: 1) denudation of the ventral ependyma (embryonic life); 2) denudation of dorsal ependyma and failure of the subcommissural organ to form Reissner fiber (first postnatal week); 3) obliteration of distal end of aqueduct; and 4) severe hydrocephalus. No evidence was obtained that NCAM is involved in the detachment of ependymal cells. The process of ependymal denudation would involve alterations of the surface sialoglycoproteins of the ependymal cells and the interaction of the latter with macrophages.

A fourth ventricle atypical teratoid/rhabdoid tumor in an infant.

Atypical teratoid/rhabdoid tumor (AT/RT), a recently established central nervous system tumor entity, occurs in children and is more malignant than medulloblastoma/primitive neuroectodermal tumors (PNET). We report here a case of AT/RT in a male infant who was 9 months old at the time of diagnosis. Magnetic resonance imaging revealed that the tumor occupied the fourth ventricle, and at surgery it was found to adhere to the floor of the fourth ventricle. After subtotal removal of the tumor mass, chemotherapy and radiotherapy were performed, but the patient died about 8 months after the diagnosis following rapid regrowth of the residual tumor. Light-microscopically, the tumor was composed mainly of nests of rhabdoid cells with fields of PNET. Occasional mesenchymal and epithelial fields were also evident. Immunohistochemically, these rhabdoid cells were positive for vimentin, epithelial membrane antigen, smooth-muscle actin, cytokeratin, and S-100 protein, and less frequently for glial fibrillary acidic protein. Electron-microscopically, the typical rhabdoid cells contained whorled bundles of intermediate filaments in their cytoplasm. Occasionally, such rhabdoid cells were covered partially by basal lamina at their stromal interface. These findings are typical of AT/RT. Although it is well known that AT/RT often arises in the posterior fossa, detailed reports of cases affecting the fourth ventricle are rare. In this case, the ultrastructural relationship between rhabdoid cells and the basal lamina, which has not so far been described in AT/RT, was of great interest when the nature of the rhabdoid cells was considered.

Reciprocal synaptic relationships between angiotensin II-containing neurons and enkephalinergic neurons in the rat area postrema.

A preembedding double immunostaining technique was used to study synaptic relationships between angiotensin-II-like immunoreactive and enkephalin-like immunoreactive neurons in the rat area postrema. The angiotensin-II-like immunoreactive neurons were detected by silver-gold intensification of the DAB reaction results while the enkephalin-like immunoreactive neurons were detected by simple ABC-DAB reaction. The synaptic relationships were reciprocal between the two neurons. Most of the synapses found between these two neurons were the presynaptic enkephalin-like immunoreactive axon terminals that made synapses on the angiotensin-II-like immunoreactive perikarya and dendrites. Both the axo-somatic and axo-dendritic synapses were symmetrical. However, although angiotensin-II-like immunoreactive axon terminals also made synapses on enkephalin-like perikarya and dendrites, the axo-somatic synapses were symmetrical, while the axo-dendritic synapses were asymmetrical. The present results confirm the presence of angiotensin-II-like immunoreactive neurons in the area postrema and suggest that these angiotensinergic neurons in the area postrema may play a role in the regulation of blood pressure via coordinated synaptic interactions with enkephalinergic neurons.