To investigate the clinical manifestations and characteristics of extruded conjunctival melanocytic mass.

A total of 33 patients who had extruded conjunctival melanocytic mass and who underwent excisional biopsy were retrospectively reviewed.

Based on the excisional biopsy results, 13 patients (40%) were diagnosed with compound nevus, nine patients (27%) with subepithelial nevus, eight patients (24%) with primary acquired melanosis without atypia, and three patients (9%) with malignant melanoma. Compound nevus was located on the temporal side of the cornea in 54% of affected cases, bulbar conjunctival in 77%, and was partially pigmented (brown) in 61%. The average size of the melanocytic mass was 24 mm when histological analysis showed melanin nevus cells in the conjunctival epithelial layer and subepithelial stromal layer. Subepithelial nevus was located on the temporal side of the cornea (56%) and in the bulbar conjunctival (78%) and had a brown color (78%). The average size of the melanocytic mass was 28 mm when histological analysis showed melanin nevus cells located only in the subepithelial stromal layer and forming nest shapes. Primary acquired melanosis without atypia was located on the temporal side of the cornea (62.5%) and bulbar conjunctival (75%) and had brown color (75%). The average size of melanin nevus cells located only in the basement membrane of the epithelial layer was 30 mm. Three of these masses were malignant melanoma, and all cases were located on the superior side of the cornea and palpebral conjunctiva. All cases were black and had an average size of 53 mm, with malignant cells observed in all layers of the conjunctiva and connective tissue.

A conjunctival melanocytic mass located on the palpebral conjunctiva, extruding onto the surface, and large in size should be suspected as malignant melanoma. In such cases, early biopsy and aggressive resection are required.