Medulloepithelioma of the brain

Last revised by Francesco Buemi on 25 Jan 2022

Medulloepitheliomas of the brain are rare, highly malignant, primitive embryonic tumors derived from the primitive medullary plate and neural tube. These tumors, once considered distinct entities, are now thought to be a pattern of embryonal tumors with multilayered rosettes. Please refer to that article for epidemiology, clinical presentation and radiology. 

In earlier editions of the WHO classification of CNS tumors, medulloepitheliomas were recognized as distinct entities and encompassed by the term "CNS primitive neuroectodermal tumor". More recent work has demonstrated that at least some of these tumors had C19MC-amplification and thus now considered embryonal tumors with multilayered rosettes (ETMR) 3,4

In the revised 4th edition (2016) of the WHO classification, the term medulloepithelioma was preserved as some tumors with this histological appearance did not have C19MC-amplification 3

In the 5th edition (2021) of the WHO classification of CNS tumors, the term medulloepithelioma no longer appears, other than mentioned in embryonal tumors with multilayered rosettes as a pattern of growth 6

Medulloepitheliomas of the brain should not be confused with medulloepithelioma of the ciliary body and medulloepithelioma of the optic disc and optic nerve, similar rare primary tumors of the eye 5

Medulloepithelioma pattern of ETMRs mimic the appearance of the primitive neural tube with cells arranged in tubular, papillary, or trabecular patterns, often with differentiation into multiple cell types (e.g. glial, neuronal or mesenchymal) 1. Mitotic figures are common with high Ki-67 proliferation index (20-80%) 6.

Medulloepitheliomas carries a very poor prognosis with a median survival of 5 months. Treatment is with maximal safe resection followed by radiotherapy with or without chemotherapy 1

In contrast, medulloepitheliomas of the ciliary body and medulloepitheliomas of the optic disc and optic nerve generally benefit from a gross-total resection and may present a good prognosis 1-4

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