A unique case of extramammary Paget's disease. Derivation from eccrine porocarcinoma?

A unique case of extramammary Paget's disease is reported that may have derived from eccrine porocarcinoma. A palm-sized erythematous plaque on the patient's pubis spread to the lower abdominal wall. The center of the lesion contained a reddish tumor. Histologic findings of the erythematous plaque showed features of extra-mammary Paget's disease. Those of the reddish tumor, however, corresponded most closely to eccrine porocarcinoma, though we could not entirely rule out that the changes corresponded to larger nests of less differentiated Paget cells. The two distinct neoplastic areas showed continuity both clinically and histologically; our case differed from epidermotropic eccrine porocarcinoma in several clinicopathologic respects. Our case suggests the possibility that extramammary Paget's disease could arise from preexisting porocarcinoma.