Loss of 5 hydroxymethylcytosine in conjunctival melanoma

Abstract

PurposeRecent studies suggest that conjunctival and cutaneaous melanoma partially share similar molecular features. In cutaneous melanoma, loss of 5 hydroxymethylcytosine (5‐hmc) was identified in tumor progression and associated with a poorer survival. We decided to assess if similar epigenetic events occur in tumor progression of conjunctival melanoma and evaluated 5‐hmc expression in benign and malignant conjunctival melanocytic proliferations.Methods5‐hmc expression was evaluated by immunohistochemistry in 32 conjunctival naevi and 36 conjunctival melanomas from respectively 32 and 31 patients. Statistical analysis was performed with JUMP 8.0 software. Immunohistochemistry was assessed by three observers. Discrepant cases were simultaneously reviewed to achieve complete agreement.Results5‐hmc was found in all the nevi. There was a significant downregulation of 5‐hmc in conjunctival melanoma compared to benign conjunctival nevi (p > 0.0001), 5‐hmc loss being identified in 52.3% of the melanoma. In the melanomas, 5‐hmc loss was significatively correlated with the depth of invasion (p = 0.0043) and local lymphatic invasion (p = 0.0149). There was no correlation with the proliferation index, local recurrences, metastasis and death.ConclusionsOur results demonstrate in vivo a significant downregulation of 5‐hmc in malignant conjunctival melanocytic proliferations suggesting that similar epigenetic modifications occur in conjunctival and cutaneous melanoma. Restauration of 5‐hmc loss in conjunctival melanoma might represent a potential therapeutical epigenetic option for this tumor.