Abstract
Purpose:
Despite improved understanding of the molecular changes in conjunctival melanoma (CoM), the underlying aetiology of this tumor remains unclear. In this study, we determined gene copy number variations (CNV) in CoM aiming to identify disease-specific genetic biomarkers to facilitate prognostication, as has been achieved in uveal melanoma.
Methods:
Ninety two patients with primary CoM seen between 2005 and 2014 were recruited in eight international ocular oncology centres. Clinical and histological data were collected. DNA was extracted from paraffin-embedded samples. Fifty-nine samples yielded sufficient DNA for Affymetrix 6.0 Single Nucleotide Polymorphism (SNP) microarray testing. SNP data were analysed by Partek Genomic suite. Patients who developed regional lymph nodes and/or systemic metastases were compared to a sex, age-matched cohort of low risk clinical and pathological criteria for dissemination and with similar follow up duration.
Results:
Over 40% of the samples showed amplifications of histone gene cluster (6p22.2), ETV1 (7p21.2), FOXQ1 (6p25.3 - 6p25.2) and SOX4 (6p22.3) and deletions in ASNS (7q21.3), CHEK2P2 (15q11.1), RET (10q11.21) and BAGE (21p11.1). CNVs in the two groups of metastatic CoM and the low risk comparative group were consistent. None of the chromosomes identified with gains or losses showed loss of heterozygosity or isodisomy. Based on the current median follow-up time of 2.5 years, no statistically significant correlation has been detected between any of the genetic alterations and features of poor outcome, i.e. caruncular involvement, epithelioid cell type or metastatic spread.
Conclusions:
This is the largest cohort of CoM samples analysed by SNP genotyping to date and describes CNVs not previously reported. Longer follow-up is required to facilitate our understanding of CoM and identification of patients at high metastatic risk.