Optic Disc Melanocytoma: A Case Report and Review

Melanocytoma is a rare benign stationary tumor that usually appears as a pigmented lesion on the optic disk. Optic Disc Melanocytoma (ODM) can compress the optic nerve or undergo necrosis, leading to ischemic axonal loss and visual field defect, similar to those caused by glaucoma. Also, ODM often displays a clinical diagnostic dilemma due to its similarities with melanoma. Some patients have undergone enucleation because of uncertainty between both pathologies. Progressive growth and malignant transformation can be documented by close monitoring of the patient’s eyes. Fundus examination and ancillary imaging procedures such as fundus photo, autofluorescence, B-scan ultrasonography, fluorescein angiography, and spectral-domain optic coherence tomography are powerful tools for ODM diagnosis and management. 

A 19-year-old female presented with a decrease in vision in the left eye for about 3 months. Her visual acuity was 20/20 and 20/80 in her right and left eyes, respectively. Funduscopic examination of the left eye showed a well-defined deeply pigmented brownish-black, dome-shaped nodular mass covered the entire optic disc with the normal-appearing overlying vitreous, macula, and surrounding retina. Short-wave autofluorescence revealed hypo-autofluorescence on the pigmented mass lesion. The patient’s condition did not change significantly over 2 years of follow-up. The diagnosis was made as ODM.

Melanocytomas grow very slowly over several years or remains stable, in contrast to malignant melanoma. Although ODM tends to have benign behavior, it may adversely affect visual function. Yearly fundus examination is necessary for monitoring growth and detecting malignant transformation. Visual loss can result from optic neuropathy or retinal vascular obstruction. In suspicious cases, close follow-up with serial fundus photographs is essential, even though the malignant transformation is exceptional.