“Melanocytoma” is a hamartomatous lesion arising from the melanocytes.[1] Optic nerve head melanocytoma (ONH-MCT) is a rare deeply pigmented dark brown or black benign tumor with feathery margins, overlying or adjacent to the optic nerve head. It may or may not involve the surrounding retina or choroid.[2] ONH-MCT occurs more often in middle-aged women but has no racial predilection. Prior reports suggest that although 32% of cases may increase in the size, only 1%–2% of cases show the malignant transformation. Hence, different investigations such as fundus autofluorescence, B-scan ultrasonography, and optical coherence tomography (OCT) play an important role in confirming the diagnosis and management.[3]
A 44-year-old man presented to our clinic with complaint of mild blurring of vision in the left eye (LE) for 2 weeks. Both eyes examination showed unaided visual acuity of 20/20, normal color vision, round, regular, and reacting pupils, and normal anterior segment. Fundus examination was within normal limits in the right eye (RE) and showed a darkly pigmented dark brown-to-black 1.5-to-2-disc diameter elevated lesion with feathery margins overlying the optic disc in the LE [Figure 1a]. There was no associated orange pigmentation or subretinal fluid around the lesion or any evidence of serous retinal detachment [Figure 1b]. LE OCT depicted a dome-shaped lesion with an anterior hyperreflective margin and shadowing of posterior structures [Figure 1c] B-scan ultrasonography of LE revealed a well-defined iso-echoic elevated lesion at the optic disc with acoustic hollowing [Figure 2a]. Contrast-enhanced axial magnetic resonance imaging of the orbit showed a focal isointense to a slightly hyperintense lesion at the level of the optic nerve head with no intraocular or intraorbital extension.[Figure 2b]. The clinical diagnosis of optic disc melanocytoma was thus confirmed. The patient was advised a monthly follow-up for 3 months and 6 months thereafter for 4 years.
Figure 1.
Composite fundus photograph. (a) Right eye. (b) Left eye showing darkly pigmented 1.5–2-disc diameter lesion on the optic nerve head with feathery margins (black arrow). (c) Left eye OCT showed a dome-shaped lesion with anterior hyperreflective margin and shadowing of posterior structures. OCT: Optical coherence tomography
Figure 2.
(a) Ultrasound B-scan ultrasonography LE showing a well-defined isoechoic elevated lesion at the optic disc with acoustic hollowing (white arrow). (b) LE orbit contrast-enhanced axial-MRI showing an iso-hyperintensity focal area overlying the posterior aspect of the globe without any extension (white arrow). MRI: Magnetic resonance imaging, LE: Left eye
It is very crucial to differentiate ONH-MT from other juxtapapillary lesions such as choroidal nevus, adenoma of retinal pigment epithelium, and malignant melanoma accurately as further treatment and prognosis differ.[3] Features which help distinguish among these include margins, color of the lesion, and presence of subretinal fluid. ONH-MCT is darkly pigmented and has irregular margins, but there is the absence of subretinal fluid or orange pigmentation.[4] Our case had features consistent with ONH-MCT, highlighting the role of ocular investigations in establishing the diagnosis.
ONH-MCT needs a regular lifelong follow-up to look for any change in visual acuity, size, shape, and consistency of the lesion. Prior reports suggest an increase in the size of the lesion in 11% of the cases at 5 years and 33% of cases after 10 years of presentation. Only 1%–2% showed the malignant transformation.[3] Further B-scan ultrasonography and OCT are useful to look for tumor growth and signs of malignant transformation (such as an increase in size, vascularity, and nodular change).[5]
The case hereby presented emphasizes the importance of early detection of ONH-MCT and the importance of ancillary investigations for differentiating it from other tumors at the optic disc with a varied management plan.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed
Financial support and sponsorship
This study was financially supported by Hyderabad Eye Research Foundation (HERF), Hyderabad, Telangana, India.
Conflicts of interest
There are no conflicts of interest.
References
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