Paget’s disease of the nipple

Paget’s disease of the nipple is unusual, and an underlying neoplasm (an abnormal growth of cells) is nearly always associated with it. The nipple and areola (the darker skin around the nipple) develop a red, scaly rash. There may be itching or burning, pain, and abnormal discharge, which can be serous (clear, watery fluid). The nipple may also become inverted (turn inwards).

The cause is malignant cells spreading along the lactiferous ducts (the tubes that carry milk to the nipple) to involve the nipple epidermis, the outer layer of the skin. The underlying cancer is usually ductal carcinoma in situ (DCIS: cancer cells still contained inside the duct, held back by the basement membrane, the thin supporting sheet beneath the lining cells) or an invasive carcinoma (one that has broken through that sheet). In Paget’s disease the malignant cells spread within the nipple epidermis without breaking through the basement membrane beneath it, although the underlying cancer in the breast may be invasive. The most widely accepted explanation of how the cells reach the epidermis is the epidermotropic theory (‘epidermotropic’ means drawn towards the epidermis): the cells migrate from the underlying breast along the lactiferous ducts.

The rash looks like eczema (inflamed, itchy skin), and the diagnosis is often delayed. It is also easily mistaken for dermatitis, so a one-sided nipple rash that does not improve with topical steroids should be regarded with high suspicion and referred to a specialist. The diagnosis is confirmed on a tissue sample (biopsy). Treatment depends on the underlying neoplasm, and the nipple and areola both need surgery.