Epidermal cell cultures from involved skin of patients with mammary and extramammary Paget's disease.

In involved epidermis, Paget cells are completely enclosed by the surrounding keratinocytes, which appear to be intact and unaltered. It is possible that the surrounding keratinocytes inhibit Paget cell proliferation. Accordingly, Paget cells might proliferate differently when cultured as an epidermal cell suspension. In this study, primary monolayer cultures of epithelial cells from involved epidermis of patients with mammary and extramammary Paget's disease were carried out to investigate whether Paget cells proliferate in the same manner as other malignant cells. Skin samples were obtained from one patient with mammary Paget's disease, and from 2 patients with extramammary Paget's disease. The epidermis was separated from the dermis with dispase, and epidermal cell suspensions were obtained with ethylenediamine tetraacetate and trypsin. A commercially available serum-free media, Keratinocyte-SFM, was used. Epithelial monolayers from the involved skin could be maintained for approximately 45 days, while keratinocytes from normal skin were maintained for approximately 35 days. The mechanism for the longer survival of the mixed cell culture of keratinocytes and Paget cells is not known. Permanent cell lines were not developed from these primary cultures. Paget cells could not be distinguished from keratinocytes by phase-contrast microscopy. The proportion of carcinoembryonic antigen (CEA) positive cells in the culture did not increase, but instead decreased. In certain areas of the dish, the CEA positive cells proliferated and accumulated like mushrooms. However, at the periphery of the dish, the Paget cells identified by immunostaining for CEA were dispersed and not clustered. These findings indicate that the influence of keratinocytes on Paget cells also occurs in cultured cells, which may explain why Paget cells survive longer than keratinocytes. In conclusion, the Paget cells in the involved epidermis do not proliferate like other malignant cells.