Aims
Conjunctival and cutaneous melanoma partially share similar clinical and molecular background. As 5-hydroxymethylcytosine (5-hmC) loss has been demonstrated in cutaneous melanoma, we decided to assess if similar changes were occurring in conjunctival melanoma.
Methods
5-methylcytosine (5-mC), 5-hmC and TET2 were respectively identified by immunohistochemistry and RNAish in 40 conjunctival nevi and 43 conjunctival melanomas. Clinicopathological correlations were established.
Results
5-mC, TET2 and 5-hmC were respectively identified in 67.5%, 95% and 100% of conjunctival nevi and in 54.5%, 40% and 53.5% of conjunctival melanomas. A significant 5-hmC and TET2 loss was identified in conjunctival melanoma comparing to nevus, as well as a significant correlation between TET2 and 5-hmC expression.
In the melanomas, 5-hmC expression was only significantly associated with local lymphatic invasion, but not with other clinicopathological parameters. There was a correlation between TET2 expression and death, but not with other clinicopathological parameters. 5- mC expression was not associated with any clinicopathological parameters.
Conclusions
We identified a significant 5-hmC loss in conjunctival melanoma similarly to cutaneous melanoma. This loss may possibly be attributed to TET2 loss or IDH1 mutations. 5-hmC loss in conjunctival melanoma may help in the differential diagnosis between atypical conjunctival nevus and conjunctival melanoma.