In the present study, we have examined whether or not the Paget cells in cases with dermal invasion or metastasis exhibit a different DNA distribution pattern to that seen in the epidermis in extramammary Paget's disease. The DNA contents of Paget cells from the epidermis and the tumor were determined by flow cytometry in two cases of extramammary Paget's disease with tumor formation, dermal invasion and metastases. The DNA histogram of Paget cells from the epidermis of two cases appeared to be close to the normal ploidy, whereas the histogram from the tumors was aneuploid in both cases. Our data suggest that the behavior of Paget cells in the epidermis is different from that in the tumor.