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B.F. Fernandes, A.N. Odashiro, V.S. Saraiva, A. Al–Kandari, S. Bakalian, M.N. Burnier, Jr.; Immunohistochemical Expression of Melanocytic Markers in Irradiated Uveal Melanoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2237.
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Tyrosinase, an important enzyme in the synthesis of melanin, and Melan–A, an antigen of melanocytic differentiation, are being used for the detection of circulating malignant cells (CMCs) by reverse transcriptase–PCR in the blood of uveal melanoma patients. However, only a few studies evaluated the co–expression of these immunohistochemical markers in primary uveal melanomas. The aim of this study was to investigate the expression of melan–A and tyrosinase in uveal melanoma as well as the influence of radiation therapy in the expression of these particular markers.
Thirty–six cases of uveal melanoma from the Henry C. Witelson Ocular Pathology Laboratory, Montreal, Canada were studied. The cases were divided in two groups based on whether or not the patient received radiation therapy prior to enucleation. The formalin–fixed, paraffin–embedded specimens were immunostained with monoclonal antibodies against tyrosinase and melan–A, and three independent investigators evaluated the expression of each marker. The chi–square test for independence was used to test for differences in expression rates of tyrosinase and melan–A between the two groups.
The expression of tyrosinase was positive in 100% of the specimens in the radiation group (15 cases) and in 95.24 % in the enucleation group (21 cases). Melan–A was positive in 93.33% of the specimens in the radiation group and in 85.71% in the enucleation group. There was no significant association between radiation status and expression of tyrosinase and melan–A. All specimens were positive for at least one of the immunohistochemical markers.
To the best of our knowledge this is the first study concluding that radiation therapy prior to enucleation does not change the expression of melanoma specific markers such as Melan–A and tyrosinase. Moreover, when tyrosinase and melan–A are used together, 100% of the formalin–fixed, paraffin–embedded samples are positive regardless of previous radiation treatment.
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