Histopathologic features of extramammary Paget disease

Extramammary Paget disease (EMPD) is characterized by large keratinocytes with abundant pale pink cytoplasm and large oval nuclei (pagetoid cytomorphology) that form nests in the epidermis. Solitary tumor cells can also be seen in the upper epidermis between the normal epidermal keratinocytes (pagetoid architecture). Duct formation is helpful in identifying the tumor, but is not always evident (H&E 200x).