PMEL and neoplasm: However, a primary malignant melanoma of the tongue can only be diagnosed when all other possible cutaneous or mucosal melanomas have been ruled out.4 Except for the absence of pan CK positivity, the immunohistochemical profile of oral malignant melanoma was comparable to that of cutaneous melanoma.5 HMB-45 is thought to be more melanoma-specific than the S100 protein.5,34 In our patient, the tumor was immunopositive for HMB-45 and the S100 protein, while negative for pan CK and desmin.