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Melanocytoma Optic Nerve Head

Synonyms

Magnocellular nevus (coined by Cogan, 1964)

Definition

As a benign, pigmented, intraocular lesion with typical clinical and histological features, melanocytoma of the optic disc is thought to develop from proliferating melanocytes normally found in the optic nerve and in the lamina cribrosa. Previously considered to be primary malignant melanomas of the optic disc, Zimmerman established the entity of “melanocytoma” indicating its benign nature.

Histology

The diagnosis can be usually made based on its typical clinical appearance (solitary uniformly dark brown or black tumor involving the inferotemporal aspect of the optic disc with feathery margins if there is infiltration into the adjacent retina) and behavior (stable or slowly growing asymptomatic lesion).

Histologically, the tumor consists of uniform deeply pigmented cells containing numerous melanosomes.  Bleaching by potassium permanganate is required to reveal the cytologic features of