Mammary and Extramammary Paget's Disease at a Glance
- Rare intraepithelial adenocarcinoma occurring in apocrine gland-bearing skin in patients over 50.
- Erythematous, scaly, eczematous plaque frequently misdiagnosed as inflammatory or infectious dermatitis.
- Most commonly affected sites: unilateral nipple/areola complex [mammary Paget's disease (MPD)], vulva, perianal skin, scrotum, and penis [extramammary PD (EMPD)].
- Most cases are associated with underlying breast carcinoma (MPD); EMPD not usually associated with underlying neoplasm but may be present in minority (15%) of cases.
Mammary Paget's disease (MPD) represents approximately 1% to 3% of breast neoplasms.1 The peak incidence is between 50 and 60 years of age and almost all reported cases occur in women.
Extramammary Paget's disease (EMPD) is a rare neoplasm that affects apocrine gland-bearing skin such as the vulva, perianal region, scrotum, and penis. The majority of patients are in the sixth through eighth decades of life.2–4 The genitals are the most commonly affected area, with EMPD representing 2% of all vulvar malignancies.3
MPD is almost always associated with underlying in-situ or invasive intraductal adenocarcinoma of the breast (up to 98% of cases in some studies).5,6 Malignant cells directly extend from the underlying tumor into the epidermis via the lactiferous ducts. Rare cases are reported to have originated primarily in the epidermis of the nipple.7
Unlike MPD, in which almost all cases have a documented underlying neoplasm, EMPD does not have a consistent histogenesis. Primary EMPD occurs in the absence of underlying malignancy and accounts for the majority of patients with the disease. These cases represent a primary intraepithelial neoplasm of apocrine origin. The malignant cells are thought to originate from intraepidermal apocrine glands or from pluripotential cells of the epidermis. The neoplasm can then invade the dermis and metastasize via lymphatic spread. In contrast, cases of secondary EMPD are associated with an underlying apocrine carcinoma or internal malignancy. These cases are due to epidermotropic spread of malignant cells from the underlying tumor. Approximately 15% of cases are associated with an underlying internal carcinoma. The most common visceral malignancies associated with EMPD are carcinomas of the rectum, bladder, urethra, cervix, and prostate.4,8,9
Both MPD and EMPD present with a long-standing history of pruritic, erythematous, scaly, or velvety patches on the breast or in apocrine-rich areas such as the groin, perineum, or axilla. Given the rather nondescript appearance, there is frequently a significant delay in diagnosis as initial treatment often involves topical steroids and/or antifungal agents for presumed inflammatory or infectious dermatitis. After continued recalcitrance to therapy, a diagnostic biopsy is performed and the correct diagnosis is made.
MPD frequently presents as a unilateral, erythematous, scaly plaque involving the nipple and/or the areola (Fig. 121-1). Ulceration and weeping with an eczematous appearance is frequently present. ...