Paget’s disease of the nipple (Fig. 18.48)
A well-defined red scaly plaque spreads slowly over and around the nipple. It is caused by the invasion of the epidermis by cells from an underlying intraductal carcinoma of the breast (Paget cells). The condition is unilateral, whereas eczema usually affects both nipples. A skin biopsy should be carried out first and if the diagnosis is confirmed mastectomy will be necessary. Extramammary Paget’s disease affects sites bearing apocrine glands and is caused by an underlying ductal carcinoma of these.