MALIGNANT-MELANOMA OF THE OPTIC-NERVE

A 67-year-old man was diagnosed as having a melanocytoma of the optic disc in the left eye. Observation during a 5-year period showed no cha nge in the lesion. At age 72 years, he had abrupt visual loss to no li ght perception in the affected left eye. Clinical examination disclose d little enlargement of the papillary tumor but ultrasonographic evide nce of optic nerve infiltration. Precontrast magnetic resonance imagin g studies disclosed a hyperintense infiltrative lesion in the enlarged left optic nerve. Enhancement features of the lesion excluded a hemor rhagic process. The eye was removed with a 22.5-mm segment of optic ne rve. Histopathologic examination showed a large, necrotic, mixed-cell malignant melanoma confined to the optic nerve. No choroidal involveme nt or viable melanocytoma cells were documented. This case stresses th at it may be difficult to differentiate a melanocytoma from a primary malignant melanoma of the optic nerve.