Aims: Toker cells (TCs) are normal components of the nipple epidermis. Because of their morphological and immunohistochemical similarities to mammary Paget cells (PCs), their presence may lead to a mistaken diagnosis of Paget's disease. The objective of this study was to identify immunohistochemical markers that are able to distinguish TCs from mammary PCs.
Methods: Nipple tissue, derived from surgical specimens following radical mastectomy for breast cancer, was obtained from 30 cases diagnosed with TCs and 30 cases of mammary Paget's disease (MPD). The tissue was examined by immunohistochemistry using antibodies to c-erbB-2, cytokeratin (CK)7, Ki-67 and oestrogen receptor (ER).
Results: TCs were consistently positive for CK7 and ER but negative for c-erbB-2. TCs either did not express Ki-67 or expressed very low levels with only 1-3 positive cells per high-power field. In contrast, MPD tended strongly to express both Ki-67 and c-erbB-2.
Conclusions: Results suggested that TCs and mammary PCs differ substantially in their expression of ER, c-erbB-2 and Ki-67, although they share immunoreactivity to CK7. Both Ki-67 and c-erbB-2 were consistently positive in mammary PCs but almost always negative in TCs, while ER was consistently positive in TCs. Therefore, a combination of these markers may allow TCs to be distinguished from mammary PCs.