Background: A more recently characterized melanocyte-specific gene, MSG-1, has been suggested as having a role in embryogenesis, melanogenesis and melanoma progression. Studies involving MSG-1 have involved cutaneous melanocytic lesions, which are different than non-cutaneous melanocytic lesions in certain pathogenetic aspects. The purpose of this study was to evaluate MSG-1 protein expression in cutaneous and mucosal melanocytic lesions, with the aim to explore its association with pigment production, malignant potential and UV light exposure.
Material/methods: Benign and malignant melanocytic lesions of cutaneous and mucosal epithelium were selected from our pathology registry (n=48). Immunohistochemistry was performed using polyclonal anti-MSG-1 antibody and standard streptavidin-biotin immunoperoxidase techniques. The staining pattern of MSG-1 was evaluated by three pathologists independently.
Results: MSG-1 protein demonstrated immunoreactivity in only one mucosal melanoma (1/20, 5%), arising in the lower lip, and showing histopathologic evidence of sun-induced tissue damage. MSG-1 also showed positivity in five cutaneous melanomas (5/14, 36%), one of which was a metastatic lesion. All mucosal and cutaneous nevi failed to express MSG-1. Melanin pigmentation, seen in 18/34 melanoma and 13/14 nevi, did not correlate with MSG-1 expression. All cases but one showing MSG-1 immunoreactivity were located in sun-exposed sites.
Conclusions: The finding of MSG-1 expression in some cases of malignant melanoma, and its absence in all benign nevi, may indicate an association with melanoma progression, particularly UV-induced lesions. Its infrequent expression in melanocytic lesions limits its diagnostic value as an immunohistochemical marker in routine pathology practice.