3.3.3 Paget’s Disease

Paget’s disease, also known as Paget´s disease of the breast or mammary Paget’s disease, is an uncommon intra-epidermal adenocarcinoma, arising from intraductal carcinoma in the breast. It can also arise from apocrine sweat glands or underlying carcinomas, for example, rectum, prostate (extramammary Paget’s disease).

The term Paget's disease of the nipple is used to distinguish the condition from Paget's disease of the bone (where bones become weak and deformed) and it is unrelated to it.

Paget’s disease occurs in less than 3% of breast cancers. The associated breast carcinoma is of the intraduct variety.

Lesions are circumscribed, erythematous, sometimes scaly, increasingly infiltrated plaques located on nipple (unilateral), axilla, groin or perianal skin. A chronic dermatitis involving one nipple must raise suspicion of Paget’s disease.

Histology/immunohistology shows large clear intra-epithelial tumour cells, PAS positive.

Paget cells are present in the epidermis. In histochemical reactions for acid mucin, such as Alcian Blue, colloidal iron and mucicarmine Mayer are detected in the cytoplasm of neoplastic cells. Immunohistochemical examination is very important to the differential diagnoses with Bowen's disease, a melanotic superficial spreading melanoma and to determine whether it is a primary or secondary disease.

Lesions are often associated with intraductal carcinoma (Paget’s disease) or adenocarcinoma (extramammary Paget’s disease). One area may become thickened and ulcerated.

Diagnosis relies on clinical features (localisation) and histology/immunohistochemistry.

Paget’s disease must be differentiated from nipple chronic dermatitis, Naevoid hyperkeratosis of the nipple, perianal dermatitis, psoriasis.

Extramammary Paget lesions can be treated with topical (imiquimod), minimally invasive (cryosurgery, photodynamic therapy) and surgical excision adjusted to tumour size and underlying disease. A multidisciplinary approach is important.