Conjunctival Melanoma

Conjunctival melanoma is a rare tumor with a high rate of recurrence. This tumor is potentially lethal. Conjunctival melanoma shares biological features and clinical behavior with its counterpart in the skin. Conjunctival melanoma can arise from primary acquired melanosis (PAM) with atypia, conjunctival nevus, nevus accompanied by PAM with atypia, or de novo. Its incidence has been increasing in recent decades and is higher in some parts of the world than in others. This tumor is more common in middle-aged and older persons and Caucasians. Ultraviolet radiation is believed to be a critical factor in conjunctival melanoma pathogenesis. This tumor may involve any part of the conjunctiva but is seen most commonly in the bulbar conjunctiva. The adjacent cornea may be affected. A confirmed diagnosis of conjunctival melanoma necessitates histological examination and often requires immunohistochemistry and molecular testing. Complete surgical excision is the primary treatment modality. Due to the high local recurrence rate, experts suggest excision, cryotherapy, brachytherapy, topical chemotherapy, with or without immunotherapy. The 10-year disease-related mortality is as high as 30%. The most important prognostic factors are tumor location, with nonbulbar tumors having a higher risk of metastasis; tumor thickness; treatment by tumor excision without adjuvant therapy; pagetoid spread; the presence of epithelioid cells; lymphatic invasion; and increased mitotic activity. Conjunctival melanomas can spread within the conjunctiva and invade the eyelid, orbit, and sinuses. They can also metastasize to the regional lymph nodes and other body parts. Spread to regional lymph nodes is often detected before systemic metastasis, and therefore, some authorities advocate sentinel lymph node biopsy in patients with high-risk conjunctival melanoma. In recent years, systemic metastases have been treated mainly by targeted therapy and immune checkpoint inhibitors.