Ependymomas are solid, neuroectodermal tumours of the ependyma that can form along the entire craniospinal axis (Kleihues et al, 2002).
single layered, ciliated epithelium
derived from the neuroepithelium of the central nervous system (CNS)
forms barriers containing polarized cells which line ventricular lumen in the developing and mature CNS
separating the cerebrospinal fluid (CSF) from the parenchyma
made up of fully differentiated glial ependymocytes, characterized by extensions of the basal membrane which attach to astrocytes.
Motile and sensory cilia cover the surface of the cells, which circulate CSF around the CNS, and microvilli absorb CSF (Del Bigio, 2010).
Ependymal malfunction leads to disturbances of CSF flow and hydrocephaly. It has also been suggested that ependymal cells filter CSF and protect the brain from potentially harmful substances within it (Kuchler et al., 1994), move cellular debris in the direction of bulk CSF flow, and disperse neural messengers (Roth et al., 1985). The ependyma underlies the tela choroidea which gives rise to the CSF producing choroid plexus (Sadler, 2010).
usually slow growing and displace, rather than invade, CNS tissue.
Cerebrospinal dissemination can occur, in which the cancer spreads via the CSF to other parts of the brain or spinal cord
although ependymomas rarely metastasize outside of the CNS.
radial glial stem cells are their origin (Merkle, et al., 2005)
Myxopapillary ependymomas and subependymomas are both well-circumscribed and occur primarily at the filum terminale and ventricles respectively. They are slow growing and localized, and only a small portion will grow large enough to cause symptoms. Following surgical resection, the tumours rarely recur and long-term prognosis is excellent (Haghighatkhah et al., 2017).
Subependymoma can also occur in the septum pellucidum and the cervical spinal cord, usually in patients over 40. Due to their mostly benign nature they are considered separate to malignant ependymoma.
Grade II ependymoma includes cellular, clear cell, tanycytic, and papillary variants. They are well delineated tumours, distinct from the surrounding parenchyma, and often extend.
Anaplastic ependymomas account for 25% of cases and have higher proliferative rates and markedly increased infiltration into surrounding tissue or dissemination into CSF, causing drop metastases.
An attempt at surgery to remove as much of the tumour as possible will be made in almost all ependymomas. Gross total resection (GTR) is only achieved in 30% of cases because vital structures are frequently involved by the tumour.
