Читать книгу Intracranial Gliomas Part II - Adjuvant Therapy - Группа авторов - Страница 19

Intracranial ependymomas are generally detected as slow-growing gliomas in children and young adults, originating from the walls of the brain ventricles. One macroscopically striking example is the so-called “plastic ependymoma,” which can fill the fourth ventricle and adjacent subarachnoid spaces extending through the foramina of Luschka and/or Magendie [3]. The tumors demonstrate morphological and ultrastructural evidence of predominantly ependymal differentiation, such as microvilli and elongated structures resembling embryologic ependymal canal, however these findings are inconsistent. The presence of perivascular pseudorosettes with a nuclear-free zone surrounding blood vessels is considered as a diagnostic hallmark of ependymomas, particularly in an infratentorial location [2, 3]. IHC for epithelial membrane antigen (EMA) is positive in two-thirds of cases, while GFAP is expressed consistently; however, it is not specific for diagnosis. Morphological distinction between ependymoma (WHO grade II) and anaplastic ependymoma (WHO grade III) is rather subjective and existing histopathological grading schemes do not work sufficiently well for their differentiation.

It is becoming evident that ependymomas are genetically heterogeneous tumors, which may be associated with differences in clinical outcomes. The updated WHO classification of CNS tumors (2016) [11] designates RELA (v-rel avian reticuloendotheliosis viral oncogene homolog A; located at 11q13) fusion-positive ependymoma (WHO grade II or III), mostly encountered in supratentorial location in children, as associated with unfavorable prognosis. Additionally, a variant “cellular ependymoma” has been abandoned [11].