Loss of antigen-processing molecules in primary orbital melanoma.

Objective: To study the antigen-processing molecules in primary orbital melanomas and correlate them with the clinicopathological features.

Methods And Materials: Antigen-processing molecules comprising the low molecular weight proteins LMP2 and LMP10, transporter associated with antigen-processing TAP1, the binding protein tapasin and the chaperone protein calnexin were analyzed by immunoperoxidase staining with monoclonal antibodies in three primary orbital melanomas. The results were correlated clinicopathologically.

Results: The three primary orbital melanomas were composed of spindle cells. LMP2, LMP10, TAP1, tapasin and calnexin were heterogeneous in the two cases with no hepatic metastasis and negative in one case with hepatic metastasis.

Conclusions: Antigen-processing molecules are decreased in orbital melanomas with increasing aggressiveness. This could have important implications for immunotherapy. This preliminary observation deserves further investigation, which may shed more light on the immune escape mechanisms of this tumor and thus make possible novel therapeutic strategies.