A perianal erythematous plaque: a quiz. Secondary extramammary Paget's disease from adenocarcinoma of the anorectal region.

An 83-year-old man with a 4-month history of an itchy perianal lesion was referred to our hospital. A physical examination revealed a round, well-demarcated, erythematous, erosive plaque involving the perianal skin (Fig. 1a). The histopathological examination of the patient’s lesion (Fig. 1b) revealed the presence of atypical tumour cells with an abundant pale-staining cytoplasm and large atypical nuclei in all layers of the epidermis. Immunohistochemically, the tumour cells were positive for carciA Perianal Erythematous Plaque: A Quiz