Genetic analysis of metastatic versus nonmetastatic conjunctival melanoma using a cutaneous melanoma gene expression panel.

Objective: Conjunctival melanoma (CJM) is a rare subtype of mucosal melanomas. Despite an increasing understanding of CJM genetics, predicting patient prognosis remains challenging. Here we sought to see if a 31-gene expression profile (31-GEP) test (i.e., DecisionDx-Melanoma) originally developed and validated for cutaneous melanoma (CM) could be useful in the prognostication of patients with CJM.

Design/participants: We performed a single-center retrospective review and gene expression profiling of 10 patients with CJM.

Methods: Deidentified archived samples of each primary tumor were sent to Castle Biosciences, where 31-GEP testing was performed. Patients were followed until death or a minimum of 5 years postexcision and monitored for tumor recurrence or metastatic spread. Mean fold change in individual gene expression was compared between nonmetastatic and metastatic groups via independent t-tests.

Results: Fifty percent of patients developed metastatic disease and had reduced overall survival (3.6 vs 9.3 months; p = 0.018). In 4 of 10 patients, two nonmetastatic and two metastatic, tumor samples passed Castle Biosciences quality control allowing for class designation. All metastatic patients and one nonmetastatic patient were designated as class 2B. The final nonmetastatic patient was designated as class 1B. In individual gene analysis, BAP1 expression was significantly reduced in the metastatic group (p = 0.03).

Conclusions: In assessing if a CM gene expression panel could aid in the risk stratification of patients with CJM, we found that the uveal melanoma-relevant gene, BAP1, may be important. Additional studies with larger sample sizes are needed to determine the relevance of this and other differentially expressed genes in CJM prognostication.