Ectopic extramammary Paget's disease affecting the upper abdomen.

We present 57-year-old man in whom ectopic extrammary Paget's disease (EMPD) affected the upper abdomen. Although the clinical appearance was suggestive of Bowen's disease or superficial basal cell epithelioma (BCE), the biopsy specimen showed EMPD histologically. Only 12 cases of ectopic EMPD have been reported (including this case). In our 20 year experience of 129 EMPD, this is the first ectopic case. Thus, the frequency of ectopic EMPD is 0.78% (one of 129) in our study. The male/female ratio in the reported 12 cases is 2: 1, nearly the same as EMPD in general (2.1: 1, in our 129 cases). The mean age of the 12 patients is 65.8 years, which is not significantly different from ordinary EMPD (66.4 years, in our 129 cases). Comparing ectopic EMPD to ordinary EMPD, clinically and histologically, we could find no difference. As they appear to be the same disease, ectopic and ordinary EMPD may share similar origins and mechanisms of occurrence. We support the hypothesis that Paget's cells originate from the remaining pluripotential germinative cells which are able to differentiate into many kinds of secreting glands.