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|Year : 1992 | Volume
| Issue : 3 | Page : 135-6
Melanocytoma of the optic disc.
MD Gahankari, R Jehangir, SS Bhatti
Dept of Ophthalmology, Seth GS Medical College, Parel, Bombay, Maharashtra.,
M D Gahankari
Dept of Ophthalmology, Seth GS Medical College, Parel, Bombay, Maharashtra.
Melanocytoma of the optic disc is a benign lesion. We report here a patient with melanocytoma who presented with gradual diminution of vision. On examination the left eye fundus showed a mass uniformly dark black in colour, on the optic disc occupying the superotemporal quadrant. The mass completely obscured the fluorescence on fluorescein angiography and was thus differentiated from malignant melanoma.
Keywords: Adult, Case Report, Diagnosis, Differential, Eye Neoplasms, diagnosis,Female, Hamartoma, diagnosis,Human, Melanoma, diagnosis,Nevus, Pigmented, diagnosis,Optic Disk,
|How to cite this article:|
Gahankari M D, Jehangir R, Bhatti S S. Melanocytoma of the optic disc. J Postgrad Med 1992;38:135
Melanocytoma of the optic disc is a benign melanotic lesion caused by proliferation of the melanocytes normally found in the uvea and occasionally in the lamina cribrosa. It is typically unilateral, stationary and rarely undergoes a malignant transformation. Melanocytomas are classically asymptomatic lesions causing no appreciable change in the visual acuity except when the tumour is large or undergoes extensive necrosis or a malignant transformation. Juxtapapillary malignant melanoma of the choroid may involve the optic disc by direct continuity, or by metastasis, if distant. Primary malignant melanoma of the optic disc is extremely rare. Malignant melanoma at times mimics a melanocytoma thereby causing diagnostic difficulty in the early stage.
A 42 year old, dark skinned, female patient presented with the complaint of gradual progressive diminution of vision in both eyes. On examination, her distant visual acuity was found to be 6/18 in both eyes. The anterior segment on slit lamp biomicroscopy was found to be normal. General and systemic examination revealed no abnormality. On dilatation, her left eye fundus showed a uniformly black, raised mass, sitting on the optic disc, occupying the superior half and partly extending in the adjacent retina for one third disc diameter in the superotemporal quadrant [Figure - 1]. The surface was smooth and the course of the blood vessels over it was undisturbed. Findings were further confirmed by Goldman's fundus contact lens examination.
The remaining portion of the posterior segment was normal. No abnormality was detected in the right eye. Intraocular pressure was 17.3 mm of Hg in both eyes. The vision improved to 6/6 for distance and N/6 for near vision in both eyes after refraction. On fluorescein angiography, the mass stood prominently totally masking the underlying disc and choroidal fluorescence. [Figure - 2]
Melanocytoma of the optic disc is rare than melanocytoma of the uvea. Opthalmoscopically, it appears uniformly black with fibrillate margins due to infiltration into the adjacent retina. Some patients have afferent papillary defects and nerve fibre bundle defects possibly due to nerve fibre layer compression. Histopathologically, the tumor cells are round or slightly polyhedral with distinct borders and small, round, normochromic nuclei. Melanocytoma commonly involves the inferotemporal aspect of the optic disc but, in this patient, it was located superiorly. On examination, the diagnosis strongly favoured was melanocytoma because of the following reasons:
a) Dark skinned female individual: melanocytoma as opposed to malignant melanoma is discovered with a relatively higher frequency in blacks and dark complexioned people.
b) Normal visual acuity: malignant melanoma that involves the optic disc usually produces a profound fall in vision with disc oedema, retinal haemorrhages and retinal detachment.
c) The mass was dark black with uniform pigmentation as against less and varied pigmentation of malignant melanoma.
d) Fluorescein angiography showed typical blocked fluorescence by the melanocytoma unlike alternating areas of hyperfluorescence and hypofluorescence in malignant melanoma.
Zimmerman in his study has reported occurrence of a sudden fall in vision with papillitis and retinal haemorrhages due to ischemic necrosis in a case of melanocytoma. Malignant melanoma was suspected and the eye was enucleated. Similar such incidences have happened in the past. Reidy et al have observed one patient, in whom a melanocytoma of the optic disc which had been followed for 17 years, suddenly transformed into a malignant melanoma.
A sudden fall in vision or increase in size should be viewed with caution for transformation to malignant melanoma, but other factors like acute vascular change, necrosis or a haematoma in a melanocytoma though rare should be kept in mind. It sometimes may be difficult to distinguish between a melanocytoma and a malignant melanoma in the early stage. Ultrasonic examination is not helpful and fluorescein angiography can be misleading. Here lies the importance of close continuous observations and serial colour fundus photography at every visit, so as to monitor the size and the rate of growth of the tumour and to guard against malignant transformation.
| :: References|| |
Zimmerman LE, Garron LK. Melanocytoma of the optic disc. Int Ophthalmol Clinic 1962; 2:431. |
|2.||Reidy JJ, Apple DJ, Steinmetz RL. Melanocytoma: nomenclature, pathogenesis, natural history and treatment, Surg Ophthalmol 1985; 29: 319-327. |
[Figure - 1], [Figure - 2]
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