Genetic Alterations in Melanocytoma Associated with Oculodermal Melanocytosis: Molecular Characteristics

Melanocytoma is a benign tumor with histologic similarity to oculodermal melanocytosis, which can undergo malignant transformation in rare cases. Melanocytoma more commonly involves the optic disc, and few cases of orbital melanocytoma have been reported. Primary orbital melanoma is a rare malignancy known to arise from pigmentary conditions, although there is little information on this tumor arising from melanocytoma. The authors present a case of malignant transformation of orbital melanocytoma in the setting of ipsilateral oculodermal melanocytosis. This case illustrates histopathologic features associated with malignant transformation and highlights the significance of GNAQ, BAP1, and specific intrachromosomal alterations occurring in oculodermal melanocytosis and melanocytoma. The molecular markers observed in this case are of interest as they have overlap with those present in uveal melanoma. This case demonstrates a timeline of genetic and molecular alterations occurring in the malignant transformation of orbital melanocytoma.