Medulloepithelioma of the ON remains a challenge because of its low frequency. The clinical presentation is similar to that of other neoformations of the ON during childhood. When its location involves the orbital portion of the ON, proptosis and optic disc swelling may occur; lesions that are more posterior can produce a progressive retrobulbar optic neuropathy . Interestingly, medulloepitheliomas that originate from an anterior location can exhibit a mass at the ON head on fundoscopic examination, and this may be a distinct clinical feature that aids in the differential diagnosis because intraocular extension is very infrequent in other tumors arising from the ON [1–3, 5–8].
Differential diagnoses of growing ON masses with reduced visual function and an intraocular component should include glioma, retinoblastoma, medulloepithelioma, and meningioma. Glioma and retinoblastoma with ON infiltration are the most frequently presumed diagnoses. Other processes, such as intraocular lesions extending onto the ON (melanocytoma, melanocytic tumors, astrocytoma, or retinal pigment epithelium proliferations), metastasis (infiltration from hematologic malignancies), or inflammatory disorders (mainly granulomatosis), are rare but should also be properly ruled out.
There are no distinct neuroimaging features of medulloepitheliomas of the ON. Calcification can be detected, as in retinoblastoma . In addition, primary ON sheath meningiomas in children can present with severely reduced vision, intraocular and intracranial invasion, and calcification detected by neuroimaging methods .
In patients with medulloepitheliomas arising from the posterior ON, mortality is usually caused by untreatable intracranial invasion or cerebral metastasis [3, 4, 9, 10]. In contrast, medulloepitheliomas arising from the anterior ON may have a better prognosis because a greater proportion of them are symptomatic, leading to earlier diagnosis [2, 4–7, 11], and they have a smaller tendency to extend into the cranium . An anterior origin may be associated with the possibility for intraocular extension that, in turn, reduces the tendency of the tumor to extend into the cranium. Moreover, localized intraocular tumors may have no direct connection to cerebrospinal fluid that allows tumors to spread. Thus, in these cases, an anterior (intraocular) approach to lesion biopsy can be considered if there is a reasonable diagnostic and therapeutic dilemma .
Our patient was remitted with presumed glioma of the ON. However, the white mass in the optic disc was not typical for a glioma, and the four-year history of a growing papillary mass was not typical for a malignant process. This could be caused by low aggressiveness of the tumor or late malignant transformation . Despite the unusualness of this presentation, this patient was successfully managed with surgery and adjuvant radiotherapy and maintained a disease-free survival of 25 years, which, to the best of our knowledge, is the longest reported to date.
The most effective management of medulloepitheliomas of the ON remains unclear. It seems that total excision is curative but, because of extension to adjacent structures, is not always possible. Adjuvant chemotherapy, radiotherapy, or extensive resection can be effective in cases of tumor infiltration at the resection margin , but there is no consensus about the regimen.