Conjunctival melanoma: outcomes based on tumour origin in 629 patients at a single ocular oncology centre

To investigate clinical features and outcomes of conjunctival melanoma classified by tumour origin.

Retrospective review of conjunctival melanoma patients at a single ocular oncology centre between April 18, 1974 and September 9, 2019. Lesions were divided into three tumour origin groups (primary acquired melanosis [PAM], nevus, and de novo) and clinical features and outcomes were compared.

There were 629 patients with conjunctival melanoma that arose from PAM (n = 476, 76%), nevus (n = 59, 9%), or de novo (n = 94, 15%). A comparison (PAM vs. nevus vs. de novo) revealed patients with tumours arising from PAM presented with older mean age (62 vs. 52 vs. 55 years, p < 0.001), worse initial logMAR visual acuity (Snellen equivalent 20/30 vs. 20/25 vs. 20/25, p = 0.03), and greater clock hour involvement (4.8 vs. 4.0 vs. 3.2, p < 0.001). Tumours arising from nevus had lower frequency of fornix (31% vs. 9% vs. 24%, p = 0.02) and tarsal involvement (29% vs. 9% vs. 26%, p = 0.046) and more frequent classification as AJCC category T1 (60% vs. 89% vs. 62%, p = 0.01). After follow-up of (57.2 vs. 68.2 vs. 51.7 months, p = 0.35), tumours arising from PAM had worse mean final visual acuity (20/50 vs. 20/40 vs. 20/40, p = 0.02) and greater frequency of visual acuity loss ≥3 lines (25% vs. 15% vs. 10%, p = 0.02). Kaplan-Meier estimates for 5-year risk showed no difference by tumour origin for visual acuity loss ≥3 lines, local tumour recurrence, exenteration, metastasis, or death.

Conjunctival melanoma most often arose from PAM, and tumour origin did not affect clinical outcomes.