An electron microscopic study of clinical Paget's disease of the nipple.

An ultrastructural study of the epidermis from eight patients with clinical Paget's disease of the nipple supports the epidermotropic theory. There was no evidence that the Paget's cells originated from keratinocytes. We propose the hypothesis that Paget's cells represent transformed ductal cells, from the subjacent lactiferous ducts of the nipple, which have migrated into the epidermis, either as neoplastic cells or as normal ductal cells with secondary in situ transformation in the epidermis.