The overall look of an anaplastic ependymoma is that of increased cellularity with microvascular proliferation. A structure resembling a perivascular pseudorosette vessel is seen in the lower right.
A cellular proliferation of cells with oval nuclei and inconspicuous nucleoli can be appreciated.
Ki-67 labeling demonstrates increased mitotic activity.
Ependymomas are WHO Grade II tumors whereas anaplastic ependymomas are WHO Grade III tumors. Anaplastic ependymomas tend to be more common in supratentorial regions and not as common in the posterior fossa (i.e. fourth ventricle) or spinal cord.
Anaplastic ependymomas are characterized by the following features: (1) increased cellularity; (2) nuclear pleomorphism; (3) high mitotic activity as demonstrated by Ki-67 labeling; (4) microvascular hyperplasia. Necrosis may be seen, but is also present in low-grade ependymomas (Fletcher).
Similar to Grade II ependymomas, the tumor-normal interface is well-demarcated rather than infiltrative. Although sheet-like growth can evoke thoughts of medulloblastoma or primitive neuroectodermal tumor, anaplastic ependymomas should still some features of ependymomas such as perivascular pseudorosettes or even true ependymal rosettes. Anaplastic ependymomas are GFAP positive, but less so than their well-differentiated counterparts (Prayson).
Despite attempts to define features of anaplasia, it appears that survival correlates with extent of resection and age of patient, and not so much on histologic features (Prayson). Prognosis is worse in children, especially in those younger than 3.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1680.
Prayson, RA. Neuropathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elvesier; 2005: 469.
Prayson R, Kleinschmidt-Demasters BK, Cohen ML. Brain Tumors. Consultant Pathology Series New York, NY: Demos Publishing: 2010: 80-3.