BETHESDA, MD. — Extramammary Paget's disease is most often found in the vulvar area and usually has an excellent prognosis, Peter J. Lynch, M.D., said at a conference on vulvovaginal diseases.
The vulva is the site of about 65% of extramammary Paget's disease (EMPD), which accounts for about 1% of all vulvar malignancies, said Dr. Lynch, emeritus professor and training program director, department of dermatology, University of California, Davis. EMPD is a disease of the elderly, affecting women 55–90 years old, with a mean age of 65. It occurs primarily among whites, although it has been reported increasingly among Asians over the past 4–5 years.
The lesions are primarily found along the “milk line,” where the sites of involvement are anywhere apocrine glands are found, including the axillae, breast, and perianal area.
Typically, extramammary Paget's lesions are similar in appearance, with an erythematous plaque that is sharply marginated. The surface of these lesions is often moist and/or crusted, but patients also may have frank erosions, he said. Whiteness in the vulvar area can be due to the absence of melanocytes, or caused by what happens when keratin gets waterlogged, since keratin is highly hydrophilic. Any disease with a buildup of keratin occurring in a wet area will have whitening in some areas, he explained.
While it may be suspected, the correct diagnosis is rarely made clinically, and generally requires a biopsy. Failure to respond to treatments, such as topical steroids and “anticandidals,” should prompt a biopsy. Diseases that may look like this condition but are less common include lichen planus and lichen sclerosis, Dr. Lynch said at the conference, sponsored by the American Society for Colposcopy and Cervical Pathology.
Histology, which is distinctive, but not pathognomonic, is characterized by clusters of pale staining cells in the epidermis, with variable extension into the hair follicles and sweat glands. However, the degree of cellular atypia can be “quite variable,” he added.
In the vulvar area, 90% of EPMD cases are primary, presenting with only intraepithelial neoplasia, and have an “excellent” prognosis, he said. Primary EPMD arises in the epidermis and does not extend into the surrounding dermis; biopsies show little (1 mm or less) or no invasion, and positive nodes or metastases are rare. (About 15% of patients with primary disease have microscopic invasion, measuring 1 mm or less).
But the prognosis is poor for those with primary disease with a deeper invasion and patients with secondary EPMD. Secondary EPMD arises from within the apocrine gland and grows for a long time, or occurs when the same or similar cells from underlying adenocarcinoma in the genitourinary or GI tract migrate upward.
Historically, the treatment of choice for EPMD has been local excision, but recurrence rates are high: For a patient with primary EPMD, with little (1 mm or less) or no invasion, the recurrence rate after a wide local excision is 35%, Dr. Lynch said.
With invasion or secondary disease, the recurrence rate is 65%, he added, noting that even after a radical vulvectomy, the recurrence rate is about 20%.
Clinical margins are not that helpful because the lesions extend beyond the visible surface. The literature currently calls for 5-cm margins, but even with Mohs micrographic surgery, recurrence rates range from 20% to 30%.
Because patients with primary in situ disease appear to have an extremely low risk of developing an associated underlying malignancy, nonexcisional treatments, such as lasers, radiotherapy, electrosurgery, photodynamic therapy or 5-fluorouracil, can be used when there is no invasion. These approaches can also be used to treat local recurrences, which usually are due to in situ disease, he said.