Mammary Paget disease (MPD) is a malignant intraepithelial condition of the nipple and periareolar skin that occurs nearly exclusively in women, usually when breast carcinoma is present. Postmenopausal women after the sixth decade of life are most commonly affected, although adolescent and elderly patients may develop MPD as well. MPD in men is extremely rare. Clinically, MPD presents as a unilateral eczematous or crusted lesion on the nipple or areola that develops slowly over months to years. Bilateral cases are rare but have been reported.

It is widely accepted that MPD is nearly always associated with underlying breast carcinoma. Malignant cells from the underlying ductal adenocarcinoma invade the nipple unit and overlying periareolar skin. The malignant cells spread through the normal epidermis in "pagetoid fashion," admixed among normal keratinocytes.

Only 1%-4% of breast carcinoma presents with MPD, but nearly 100% of MPD is associated with an underlying breast carcinoma (ductal carcinoma in situ [10%] or infiltrating carcinoma [90%]).

The malignant cells of MPD express the same apomucins and possess the chromosomal aberrations of the underlying breast cancer. The condition is detected on biopsy using the same immunohistochemical stains employed in breast carcinoma, such as cytokeratin 7 (CK7).

Presence of a palpable mass in the breast, lymphadenopathy, younger age (less than 60 years), and aggressive histology may be associated with poor prognosis. The presence of a palpable mass in the breast may represent invasive carcinoma rather than in-situ stage.

Treatment requires referral to a breast oncologist and oncologic surgeon to detect and manage the underlying breast carcinoma.

Related topics: cutaneous presentations of breast cancer, female breast cancer, male breast cancer