Extracranial teratoid medulloepithelioma: A pelvic observation with genetic and epigenetic findings.

In the latest version of the World Health Organization Classification (WHO) of Central Nervous System Tumors, the terminology "medulloepithelioma" has disappeared as a distinct tumor type in favor of "embryonal tumor with multilayered rosettes (ETMR)", characterized by frequent alterations of C19MC. However, medulloepithelioma persists in the current WHO classification of eye tumors, where two variants exist (teratoid and non-teratoid), harboring frequent DICER1 mutations. DNA-methylation profiling has demonstrated that ETMR and intraocular medulloepitheliomas represented two distinct methylation classes. Outside the CNS and the eye, exceptional observations of medulloepitheliomas have been reported, most of them before the genetic and epigenetic eras. Herein, we report a pediatric case of a presacral tumor classified as a teratoid medulloepithelioma with genetic and epigenetic charaterizations. Using DNA-methylation profiling analysis, the tumor was classified between ETMR, non C19MC-altered, and intra-ocular medulloepithelioma, arguing for a potential distinct cell origin, not represented in the current epigenetic classifiers.