Is MAGE-1 expression in metastatic malignant melanomas really helpful?

Melanoma antigen-encoding gene (MAGE-1) has been introduced as a sensitive immunohistochemical marker to aid in the diagnosis of malignant melanomas, in particular, those that are HMB-45 negative. Our goal was to determine the consistency of positive staining in melanomas on the basis of the usefulness of MAGE-1 in comparison with tyrosinase and MART-1. We studied 56 malignant melanomas using immunohistochemical markers to MAGE-1, tyrosinase, MART-1, HMB-45, and S-100. Six of 17 HMB-45-negative cases were strongly positive for MAGE-1 (35%), while 9 of 39 HMB-45-positive cases were positive for MAGE-1 (23%), overall, 27% positivity (n = 56). Tyrosinase and MART-1 were both strongly positive in 42 of 56 cases (75%). Fifty-two of 56 cases were strongly positive for S-100 (93%). We found MAGE-1 to be less sensitive than described in other studies, and overall, not very helpful, especially as a predictor of aggressive behavior. Although MAGE-1 expression has been considered as a target for immunomodulation therapy, our findings do not indicate consistent expression of this epitope in a majority of melanomas. S-100 protein, tyrosinase, and MART-1 immunomarkers were more frequently positive in our melanoma cases and appear to constitute a useful panel of markers to aid in the diagnosis of metastatic malignant melanomas, especially in patients with an unknown primary.