KRT5 and neoplasm: Immunohistochemistry testing of the tumor in the case described above was positive for S-100, mammaglobin, low-molecular-weight cytokeratin, cytokeratin AE1/AE3, vimentin, and GATA-3 and negative for cytokeratin 5/6, p63, CD45, PAX-8, and CD68 consistent with SC.