[Lipomatous ependymomas of the posterior fossa. An infrequent and little-known subtype. A case report and review of the literature]. / Ependimomas lipomatosos de la fosa posterior. Un subtipo muy infrecuente y poco conocido. Presentación de caso y revisión de la literatura.

Ependymomas are well defined glial tumours composed of uniform small cells with round nuclei in a fibrillar matrix. They have characteristic perivascular acellular areas (pseudorosettes) and, in some cases, ependymal rosettes. The three most well-known histological phenotypes are papillary, clear-cell and tanycytic. The WHO classification includes rare cases of ependymoma with lipomatous metaplasia. Lipomatous ependymomas of the posterior fossa are extremely rare; we only found 7reports of cases in adults. They usually arise in the fourth ventricle and may extend into the cerebellum, when they often show extensive vacuolization, pushing the nucleus to the periphery and giving rise to a signet-ring cell appearance. Radiologically, there are few findings characteristic of these tumours. Immunohistochemistry is essential to differentiate this subtype from other more common lesions, such as metastatic adenocarcinoma, especially from breast, intestine and kidney.

Ependimomas lipomatosos de la fosa posterior. Un subtipo muy infrecuente y poco conocido. Presentación de caso y revisión de la literatura / Lipomatous ependymomas of the posterior fossa. An infrequent and little-known subtype. A case report and review of the literature

Los ependimomas son tumores gliales bien circunscritos compuestos de células pequeñas uniformes con un núcleo redondo en una matriz fibrilar. Se caracterizan por zonas anucleadas perivasculares (pseudorrosetas) y, en algunos casos, rosetas ependimarias. Tres fenotipos histológicos son los más reconocidos: papilar, de células claras y tanicítico. La OMS reconoce casos raros de ependimomas con metaplasia lipomatosa. Los ependimomas lipomatosos de fosa posterior son extremadamente infrecuentes, y en nuestra búsqueda hemos encontrado 7casos reportados en la literatura (excluyendo niños). Se originan habitualmente del 4.° ventrículo y podrían presentar extensión cerebelosa. Estos suelen presentar extensa vacuolización empujando el núcleo a la periferia y simulando la apariencia de «signet-ring cells» (células en anillo de sello). Radiológicamente hay pocos hallazgos que sean característicos de este tipo de tumores. La inmunohistoquímica es decisiva para no confundir esta variante con lesiones más comunes, como el adenocarcinoma metastásico, especialmente los de mama, intestino y renal.(AU)

Ependymomas are well defined glial tumours composed of uniform small cells with round nuclei in a fibrillar matrix. They have characteristic perivascular acellular areas (pseudorosettes) and, in some cases, ependymal rosettes. The three most well-known histological phenotypes are papillary, clear-cell and tanycytic. The WHO classification includes rare cases of ependymoma with lipomatous metaplasia. Lipomatous ependymomas of the posterior fossa are extremely rare; we only found 7reports of cases in adults. They usually arise in the fourth ventricle and may extend into the cerebellum, when they often show extensive vacuolization, pushing the nucleus to the periphery and giving rise to a signet-ring cell appearance. Radiologically, there are few findings characteristic of these tumours. Immunohistochemistry is essential to differentiate this subtype from other more common lesions, such as metastatic adenocarcinoma, especially from breast, intestine and kidney.(AU)

Spectrum of sublytic astrocytopathy in neuromyelitis optica.

Neuromyelitis optica is an autoimmune inflammatory disorder targeting aquaporin-4 water channels in CNS astrocytes. Histopathological descriptions of astrocytic lesions reported in neuromyelitis optica so far have emphasized a characteristic loss of aquaporin-4, with deposition of IgG and complement and lysis of astrocytes, but sublytic reactions have been underappreciated. We performed a multi-modality study of 23 neuromyelitis optica autopsy cases (clinically and/or pathologically confirmed; 337 tissue blocks). By evaluating astrocytic morphology, immunohistochemistry and AQP4 RNA transcripts, and their associations with demyelinating activity, we documented a spectrum of astrocytopathy in addition to complement deposition, microglial reaction, granulocyte infiltration and regenerating activity. Within advanced demyelinating lesions, and in periplaque areas, there was remarkable hypertrophic astrogliosis, more subtle than astrocytic lysis. A degenerative component was suggested by 'dystrophic' morphology, cytoplasmic vacuolation, Rosenthal fibres and associated stress protein markers. The abundance of AQP4 mRNA transcripts in sublytic reactive astrocytes devoid of aquaporin-4 protein supported in vivo restoration following IgG-induced aquaporin-4 endocytosis/degradation. Astrocytic alterations extending beyond demyelinating lesions speak to astrocytopathy being an early and primary event in the evolving neuromyelitis optica lesion. Focal astrocytopathy observed without aquaporin-4 loss or lytic complement component deposition verifies that astrocytic reactions in neuromyelitis optica are not solely dependent on IgG-mediated aquaporin-4 loss or lysis by complement or by IgG-dependent leucocyte mediators. We conclude that neuromyelitis optica reflects a global astrocytopathy, initiated by binding of IgG to aquaporin-4 and not simply definable by demyelination and astrocytic lysis. The spectrum of astrocytic morphological changes in neuromyelitis optica attests to the complexity of factors influencing the range of astrocytic physiological responses to a targeted attack by aquaporin-4-specific IgG. Sublytic astrocytic reactions are no doubt an important determinant of the lesion's evolution and potential for repair. Pharmacological manipulation of the astrocytic stress response may offer new avenues for therapeutic intervention.