CK is a mixture of two antibodies, AE1/AE3, that recognize members of the acidic and basic subfamily of cytokeratins, and AE1/AE3 can label almost all epithelial cells. AE1/AE3 help detect lymph node micrometastases and can be used for squamous cell tumors (including spindle cell variant), adenocarcinoma, transitional cell carcinoma, small cell carcinoma, carcinoid, pleomorphic adenoma (epithelial component) , thymoma, mesothelioma (including sarcomatoid components), chordoma, germ cell tumors (excluding seminoma), synovial sarcoma and epithelioid sarcoma diagnosis.