Diagnosis of the origin of an epibulbar melanocytic tumor with molecular genomics.

BACKGROUND:Uveal melanoma (UM) and conjunctival melanoma (CM) are distinct entities with different etiologies and genetic background. We present a case of an atypical subconjunctival melanoma arising from a blue nevus. PATIENTS AND METHODS:A 61-year-old female presented with a partially melanocytic epibulbar mass with surrounding episcleral pigmented spots. The lesion was detached from the overlying conjunctiva without an intraocular component. Excisional biopsy revealed a predominantly epithelioid melanoma, that was suggested to be metastasic, although there was no evidence of a primary melanoma elsewhere. RESULTS:Molecular analysis identified GNAQ and BAP1 pathogenic variants, which strongly suggested the diagnosis as a primary epibulbar melanoma arising from episcleral blue nevus. CONCLUSION:This case demonstrates the value of tumor molecular analysis using Next Generation Sequencing (NGS) for differentiating the origin of an unusually located ocular melanoma.