Mutational Landscape and Outcomes of Conjunctival Melanoma in 101 Patients

To evaluate targetable mutations and molecular genetic pathways in conjunctival melanoma with clinical correlation.Observational case series.Patients with conjunctival melanoma.Mutational profile of the tumor by next-generation sequencing (NGS), alternative lengthening of telomeres (ALT) by fluorescence in situ hybridization (FISH), and ATRX immunohistochemistry. Outcomes at 2 years and 5 years of tumor-related metastasis and death were recorded.Of the 101 patients, mean age at presentation was 60 years, 52% were male, and 88% were White. The NGS panels initially targeted BRAF only (n = 6, 6%), BRAF/NRAS (n = 17, 17%), and BRAF/NRAS/NF1 (n = 10, 10%). Sixty-eight tumors were tested with the expanded 592-gene panel. Next-generation sequencing identified high-frequency mutations in NF1 (29/74, 39%), BRAF (31/101, 31%), NRAS (25/95, 26%), and ATRX (17/68, 25%). Of those with an ATRX mutation, 12 (71%) had an additional NF1 mutation. A subset analysis of 21 melanomas showed that the ATRX mutation was associated with loss of ATRX protein expression and ALT. Loss of ATRX expression and ALT were present in both intraepithelial and invasive tumors, suggesting that an ATRX mutation is an early event in conjunctival melanoma progression. The NF1 and ATRX mutations were associated with tarsal (vs. nontarsal) tumors (NF1: 28% vs. 9%, P = 0.035, ATRX: 41% vs. 14%, P = 0.021) and orbital (vs. nonorbital) tumors (ATRX: 24% vs. 2%, P = 0.007). ATRXMUT (vs. ATRXWT) tumors were associated with a lower 2-year rate of metastasis (0% vs. 24%, P = 0.005). NRASMUT (vs. NRASWT) tumors were associated with a greater 2-year rate of metastasis (28% vs. 14%, P = 0.07) and death (16% vs. 4%, P = 0.04), with a 5-fold increased risk of death (relative risk, 5.45 [95% confidence interval, 1.11-26.71], P = 0.039).This study confirms the high frequency of previously documented BRAF and NRAS mutations and recently reported ATRX and NF1 mutations in conjunctival melanoma. An NRAS mutation implied increased risk for metastasis and death. Loss of ATRX and ALT may be early events in conjunctival melanoma development.