LAUSR

ABSTRACT 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.