Amelanotic Melanoma Arising within Conjunctival Melanocytic Intraepithelial Neoplasia Sine Pigmento

A 61-year-old man was referred for a vascularized lesion of the conjunctival limbus suspicious for carcinoma in situ (Fig A). However, excisional biopsy demonstrated superficially invasive melanoma arising within conjunctival melanocytic intraepithelial neoplasia (C-MIN). Both the epithelial and invasive components lacked visible melanin. Roughly 80% of the conjunctival epithelium was replaced by atypical melanocytes (Fig B); that expressed MART-1 (melanocyte antigen marker; Fig C). The tumor extended 0.6 mm into substantia propria (Fig D).