Large Choroidal Melanocytoma Simulating Choroidal Melanoma: A Difficult Differential Diagnosis and an Inevitable Enucleation

Abstract

Purpose. To describe a case of choroidal melanocytoma mimicking a melanoma. Methods. Retrospective case report. Patient. A 48-year-old Moroccan woman presented with progressive, painless decreased vision in her left eye for 2 months. Results. Her visual acuity was light perception in the left eye and 20/20 in the right one. Fundus examination and fluorescein angiography of the left eye showed a total retinal detachment with a large superior brownish mass. The clinical examination, B-scan ultrasonography, and magnetic resonance imaging all suggested a malignant melanoma. Consequently, the eye was enucleated. The histopathology later revealed a benign melanocytoma of the choroid. Discussion. Melanocytoma is a rare benign pigmented tumor. It is classically described as a tumor of the optic nerve head, but there are some exceptional case reports of uveal tract locations (iris, ciliary body, and choroid). In such cases, it can be difficult to clinically differentiate a melanocytoma from a malignant melanoma.

The pigmented puzzle: A case of cilio-choroidal melanocytoma

“…Whereas melanomas are brown with non-uniform distribution and show surface irregularities and orange pigmentation. 10,11 Both melanomas and melanocytomas are slow-growing tumours so clinically very tough to distinguish from each other. 10,12 Histopathology is the diagnostic modality.…”

“…MRI orbit is not considered as superior to other diagnostic modalities due to equivocal features of uveal melanoma and uveal melanocytomas. 11,12 Diagnostic fine needle aspiration biopsy is usually preferred in ciliary body mass to differentiate melanoma from other pigmented masses. Can be done either by trans scleral or trans-vitreal route.…”

“…In melanoma, the cytology should reveal melanoma cells, if it reveals melanocytoma cells it is possible that sampling error or foci of tumor mass is missed. 11,15 Melanocytomas are slow-growing rarely affect the vision and have rare malignant transformations seen in 1-2% of cases. 4,7 So, diagnosed cases of melanocytoma can be observed at 3 monthly intervals and thereafter 1 yearly.…”

Large ciliary body melanocytoma with pseudocysts: a case report

“…This difficulty is reflected by some authors stating that most melanocytomas are low reflective and others that they are usually high reflective [ 2 , 4 ]. The internal structure of intraocular tumors is best evaluated by standardized A-scan and is directly correlated to the histologic architecture of lesions [ 1 , 3 ].…”

“…Most melanocytomas are under 2 mm in thickness which makes it difficult to evaluate internal reflectivity by ultrasound [ 1 , 2 ]. However, standardized A-scan is an important diagnostic tool in the differentiation of ciliary body melanocytomas from melanomas [ 3 ].…”