Expression of milk fat globule epidermal growth factor-VIII may be an indicator of poor prognosis in malignant melanoma

Background Milk fat globule epidermal growth factor-VIII (MFG-E8) is a secreted protein that binds phosphatidylserine and promotes apoptotic cell ingestion by phagocytes, mediating the immune tolerance and maintenance of homeostasis. A recent study has shown that MFG-E8 expression in human melanoma is increased with tumour progression; however, the effect of its expression on patient survival has not yet been clarified. Objective To analyse MFG-E8 expression in melanoma, and to determine whether it can serve as a marker for diagnosis, tumour progression and/or prognosis. Methods MFG-E8 expression was examined by immunohistochemistry in 60 primary melanomas, 22 metastatic lesions and 30 benign naevi. The following clinicopathological variables were evaluated: age, gender, histological type, tumour site, Breslow thickness, Clark's level, the presence or absence of ulceration and tumour-infiltrating lymphocytes, and survival periods. Statistical analyses were performed to assess associations and melanoma-specific survival. Results MFG-E8 expression was significantly higher in primary and metastatic melanoma than in naevus. Furthermore, it increased according to tumour progression and metastasis. Patients with MFG-E8 expression in primary tumours had significantly shorter survival periods than those without MFG-E8 expression. Univariate and multivariate analyses revealed that MFG-E8 expression was a statistically significant and independent prognostic factor. Conclusion MFG-E8 expression may serve as a tumour progression marker and can predict an unfavourable prognosis in patients with melanoma.