BACKGROUND: The tumour suppressor gene product, p16, is often inactivated during melanoma malignant progression. Although the importance of p16 in melanomas is well documented, its relationship with cyclin D1, beta-catenin and ultraviolet radiation (UVR) remains unclear. AIM: To determine the role of these cell cycle-related proteins and high-risk sun exposure in the biological behaviour of melanocytic lesions. METHODS: We used immunohistochemistry to examine 28 melanocytic naevi (MN; 9 congenital and 19 acquired types) and 24 primary cutaneous malignant melanomas (CMM; 19 nodular melanomas, 3 lentigo maligna melanomas, 1 acral lentiginous melanoma and 1 superficial spreading melanoma) for the presence of p16, cyclin D1 and beta-catenin. The melanocytic lesions were classified into two groups to examine the effects of UVR on these three proteins: high risk of sun exposure (chronically sun damaged; CSD), or low risk of sun exposure (nonchronically sun damaged; non-CSD). We evaluated the relationship between the production of these proteins and the histopathological and clinical characteristics of the lesions. RESULTS: Production of p16 was repressed in most CMM, but not in MN (P < 0.0001). Cyclin D1 was overproduced in CMM but not in MN, and beta-catenin was frequently overproduced both in MN and CMM. Overproduction of beta-catenin was not common in CSD melanocytic lesions, but was more frequent in non-CSD melanocytic lesions (P = 0.027). CONCLUSION: An immunohistochemical panel including melanocytic markers enriched by p16 and cyclin D1 could be used to differentiate some borderline melanocytic lesions. In addition, the Wnt/beta-catenin pathway was more frequently activated in non-CSD than in CSD melanocytic lesions.
BACKGROUND: The tumour suppressor gene product, p16, is often inactivated during melanoma malignant progression. Although the importance of p16 in melanomas is well documented, its relationship with cyclin D1, beta-catenin and ultraviolet radiation (UVR) remains unclear. AIM: To determine the role of these cell cycle-related proteins and high-risk sun exposure in the biological behaviour of melanocytic lesions. METHODS: We used immunohistochemistry to examine 28 melanocytic naevi (MN; 9 congenital and 19 acquired types) and 24 primary cutaneous malignant melanomas (CMM; 19 nodular melanomas, 3 lentigo maligna melanomas, 1 acral lentiginous melanoma and 1 superficial spreading melanoma) for the presence of p16, cyclin D1 and beta-catenin. The melanocytic lesions were classified into two groups to examine the effects of UVR on these three proteins: high risk of sun exposure (chronically sun damaged; CSD), or low risk of sun exposure (nonchronically sun damaged; non-CSD). We evaluated the relationship between the production of these proteins and the histopathological and clinical characteristics of the lesions. RESULTS: Production of p16 was repressed in most CMM, but not in MN (P < 0.0001). Cyclin D1 was overproduced in CMM but not in MN, and beta-catenin was frequently overproduced both in MN and CMM. Overproduction of beta-catenin was not common in CSD melanocytic lesions, but was more frequent in non-CSD melanocytic lesions (P = 0.027). CONCLUSION: An immunohistochemical panel including melanocytic markers enriched by p16 and cyclin D1 could be used to differentiate some borderline melanocytic lesions. In addition, the Wnt/beta-catenin pathway was more frequently activated in non-CSD than in CSD melanocytic lesions.