HLA class II antigen expression in uveal melanoma: correlation with clinicopathological features

The authors examined the immunoexpression of human leukocyte (HLA) class II antigen in uveal melanomas and correlated with the cell types, largest tumour dimension and extrascleral invasion. HLA class II antigen expression was analysed in 45 primary uveal melanoma lesions by immunoperoxidase staining with monoclonal antibody. Immunoanalysis was done by a semi-quantitative method according to the International Histocompatibility Working Group, Project description. The results were correlated clinicopathologically. Among the 45-uveal melanomas, 17 were spindle cell types, 16 were mixed cell types and 12 were epithelioid cell types. Among the 35 tumours with no extrascleral extension, HLA class II antigen was decreased in (100%) 35/35 tumours. Among the 10 tumours with extrascleral extension, HLA class II antigen was positive in the 60% (6/10) tumours with liver metastasis and decreased in 40% (4/10) tumours with no liver metastasis. HLA class II antigen was negative in 94% (16/17) spindle cell melanomas. Decreased HLA class II immunoreactivity in tumours with no extrascleral extension was significant (P<0.001). Negative HLA class II immunoreactivity in the spindle cell melanoma was significant (P<0.001). There was no correlation with largest tumour diameter and immunoreactivity. HLA class II antigen is an independent prognostic marker in uveal melanoma. Thus, HLA class II antigen expression in uveal melanoma in relation to prognosis and cell types are similar to HLA class I antigen expression, where downregulation and presence of spindle cell melanoma correlates with favourable outcome. This may have important implications with respect to proposed T cell based immunotherapy.