Conjunctival melanoma: Insights into classification, outcomes, and biomarkers

Abstract

Conjunctival melanoma is quite rare, estimated at approximately 0.5 incidence per 1 million persons per year. This malignancy arises from a pre-existing nevus (7%), primary acquired melanosis (74%), or de novo without pre-existing condition (19%) and develops most often in patients with Fitzpatrick skin types I (23%) and II (62%). At initial presentation, the tumor size is approximately 13 mm in cross-sectional diameter and has 3-mm thickness, involving the bulbar (97%), forniceal (30%), tarsal (28%), or caruncular (11%) regions, often with corneal (54%) and rarely with orbital (4%) involvement. According to the eighth edition of the American Joint Committee on Cancer (AJCC), the tumor is classified as T1 (63%), T2 (18%), T3 (20%), and T4 (0%). Outcomes depend on several factors including patient age, AJCC classification, orbital invasion, and type of initial surgery, whereas tumor origin and Fitzpatrick skin type do not appear to impact outcomes. Older patients (≥70 years of age) demonstrate larger tumors, greater recurrence, and greater vision loss. Analysis of 425 patients by AJCC classification (T1 versus T2 versus T3) revealed increasing T category with greater lymph node metastasis (3% versus 13% versus 25%; P < .001), tumor-related systemic metastasis (13% versus 45% versus 40%; P < .001), and tumor-related death (8% versus 22% versus 37%; P < .001). Data of patients with orbital invasion revealed significantly greater 10-year rates of exenteration (P < .001), distant metastasis (P = .0005), and death (P = .001). Studies have demonstrated biomarkers related to conjunctival melanoma include mutations in BRAF, NRAS, ATRX, and NF1. Future therapies might be directed against these mutations or with small-molecule inhibitors and/or immunotherapy. In summary, conjunctival melanoma is a rare but ominous malignancy, imparting moderate risk for lymph node and systemic metastasis as well as death, depending on tumor features and classification. The first surgery is highly important in prevention of tumor seeding, recurrence, and metastasis.