Expression of HLA class I, beta(2)-microglobulin and HLA class II antigens in primary orbital melanoma

Major histocompatibility antigens (MHC) play a crucial role in the recognition of tumor cells by the immune system. There is not much information on the role of MHC molecule expression in primary orbital melanomas. In the present study, the authors examined the expression of human leukocyte antigen (HLA) class I, beta(2)-microglobulin (beta(2)-m) and HLA class II antigens in primary orbital melanoma and correlated this with the clinical and pathological findings. HLA class I antigen, beta(2)-m and HLA class II antigen expression were evaluated immunohistochemically in three primary orbital melanomas and correlated with cell type and metastasis. Immunohistochemistry showed heterogeneous expression of HLA class I, beta(2)-m and HLA class II antigen in two cases with no liver metastasis and negative expression in one case with liver metastasis. 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.