Aims Toker cells are clear cells present in the squamous epithelium of the nipple of some women. In contrast to squamous epithelium, they are cytokeratin 7 (CK7) positive. The origin of these cells is not completely understood. It has been suggested that they may represent abortive glands or migratory ductal cells; and may be precursors of Paget's disease of the nipple. Our aim was to investigate the incidence and distribution of Toker cells and their relationship with lactiferous ducts.

Methods We examined nipple sections from 100 consecutive mastectomies performed at Charing Cross hospital. New sections were stained for CK7 using the immunoperoxidase technique.

Results Toker cells were identified in 11 cases. They were always clustered within the squamous epithelium superficial to sebaceous glands with no relationship with lactiferous ducts. Two cases in the study had Paget's disease and these were not associated with underlying sebaceous glands.

Conclusions This study suggests that Toker cells are more likely to be developmentally related to sebaceous glands rather than lactiferous ducts. This raises doubts about the presence of a relationship between Toker cells and the common forms of Paget's disease, as the latter are commonly seen in association with ductal carcinoma in situ (DCIS) involving underlying lactiferous ducts. Toker cells, however, may be related to a less common form of Paget's disease which is not associated with underlying DCIS.