MPO and melanoma: Moreover, immunohistochemical stains for monoclonal cytokeratin 7, cytokeratin 20, epithelial membrane antigen (EMA), myeloperoxidase (MPO), calretinin, mesothelial cell, actin, desmin, human melanoma black-45 (HMB-45), melanoma, CD3, CD15, CD30, CD31, and anaplastic lymphoma kinase (ALK) were all negative.