Iris and anterior chamber angle melanoma masquerading as benign melanocytic lesion.

Purpose: Demonstrates the importance of integrating clinical findings, immunohistochemistry, and next-generation sequencing of somatic mutations in differentiating complex ocular melanocytic lesions. This study highlights distinct differences between benign conjunctival nevus, iris melanoma with extrascleral extension, and conjunctival melanoma with intraocular invasion. Observations: A 62-year-old male presented with painless vision loss and multiple pigmented lesions on the ocular surface. Initial impression was a benign conjunctival nevus but concerning for melanoma due to secondary changes of vision loss and increased intraocular pressure. Further investigation revealed an iris melanoma involving the anterior chamber angle with extrascleral extension. Enucleation confirmed atypical melanocytic cells infiltrating the iris stroma, anterior chamber angle, sclera, and conjunctiva. Immunohistochemistry showed SRY-Box Transcription Factor 10 (SOX10) and melanoma antigen (Melan-A) positivity. Gene sequencing identified a Guanine nucleotide-binding protein, alpha-11 (GNA11) mutation, suggesting uveal origin. Conclusions and importance: Highlights the value of a comprehensive diagnostic approach in evaluating ocular melanocytic lesions. The progression from an initial impression of benign conjunctival nevus to the discovery of iris melanoma with extrascleral extension emphasizes the need for thorough investigation, especially when pathological changes such as increased intraocular pressure and vision loss occur.