Paget's disease is an eczematoid change of the nipple associated with an underlying breast malignancy and it is present in 1-2% of patients with breast cancer. In half of these patients, it is associated with an underlying mass lesion and 90% of such patients will have an invasive carcinoma. 30% of patients without a mass lesion will still be found to have an underlying carcinoma. The remainder will have carcinoma in situ.

Paget's disease differs from eczema of the nipple in that it involves the nipple primarily and only latterly spreads to the areolar (the opposite occurs in eczema).

Diagnosis is made by punch biopsy, mammography and ultrasound of the breast.

Treatment will depend on the underlying lesion.