Cutaneous mucinous carcinoma arising in extramammary Paget disease of the perineum.

We present the case of a 74-year-old woman with a 7-year history of an expanding vulval and perianal erythematous plaque, which failed to respond to topical treatments in the community. Biopsy of the affected skin showed typical features of extramammary Paget disease. No underlying associated malignancy was identified. After 2 months of treatment with 5% topical imiquimod, the patient developed a new tender nodule in the perineal region. Histological examination revealed a mucinous carcinoma, which, after careful clinical assessment, was deemed to be a primary cutaneous mucinous carcinoma. This is the second reported case of a primary cutaneous mucinous carcinoma arising on a background of extramammary Paget disease of the vulva and perineum.