[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)