A case of extramammary Paget's disease mimicking pemphigus vulgaris on histologic examination.

We present a case of extramammary Paget's disease (EMP) on the vulva of a 77-year-old female that on histologic examination resembled pemphigus vulgaris. The diagnosis of EMP was established with the help of a periodic acid-Schiff stain and immunophenotyping. Ultrastructural studies revealed no desmosomes between tumor cells and keratinocytes and only rare desmosomes between adjacent tumor cells. A high number of tumor cells with scant desmosomes may be the ultrastructural correlate with cellular discohesion in the lower epidermis and with the histologic resemblance to pemphigus vulgaris.