Paget cells express cytokeratins typical of glandular epithelia.

The expression of cytokeratins in Paget cells in mammary and extramammary Paget's disease was studied using different keratin antibodies and immunofluorescence microscopy. Antibodies to epidermal keratin did not react with the Paget cells but stained the surrounding epidermis. Two monoclonal cytokeratin antibodies (PKKI and RGE 53), which reacted typically with simple glandular epithelia in normal tissues, brightly stained the Paget cells and left the surrounding epidermal cells unstained. The results indicate that Paget cells are derived from mammary or sweat duct epithelium rather than from epidermal cells.