Comparative immunohistochemical oestrogen receptor analysis in primary and metastatic uveal melanoma

The investigation reported here was carried out to determine the oestrogen receptor status of metastatic and primary uveal melanomas. A series of 23 primary and 24 metastatic formalin-fixed paraffin-embedded choroidal melanomas were analysed immunohistochemically with the monoclonal antibody (MAb) 1D5 using the avidin-biotinylated peroxidase method and antigen retrieval with microwaves. Melanophages were identified with MAb PG-M1 to macrophages. None of the primary or metastatic melanomas contained tumour cells that would have shown a nuclear immunoreaction for oestrogen receptors with MAb 1D5. However, in 20 of the 23 primary tumours and in 14 of the 24 metastases a variable number of infiltrating cells showed a strong positive cytoplasmic immunoreaction with MAb 1D5. The cells contained pigmented cytoplasmic granules that resisted bleaching of melanin and their cytoplasm was strongly labelled with MAb PG-M1, identifying them as cross-reacting macrophages. Oestrogen receptors can not be used as a prognostic indicator if anti-oestrogen therapy is considered for treatment of metastatic uveal melanoma. However, because anti-oestrogens also act by other mechanisms on both tumour and host tissues, the lack of oestrogen receptors does not automatically negate their therapeutic effect in disseminated melanoma.