Extramammary Paget's Needs More Than Mohs

WAIKOLOA, HAWAII – Extramammary Paget’s disease poses a particular challenge because of its multifocal/multicentric nature.

"What you see with extramammary Paget’s is not necessarily what you get," Dr. Theodore Rosen cautioned at the Hawaii Dermatology Seminar sponsored by Skin Disease Education Foundation (SDEF).

This is an uncommon neoplasia that’s typically described as an erythematous, erosive, itchy patch or plaque having a strawberries-and-cream appearance. Yet there may be other areas of subclinical involvement at a distance from the obvious lesion. 

"That’s why Mohs surgery for this condition may be difficult without something being done in advance," said Dr. Rosen, professor of dermatology at Baylor College of Medicine, Houston. 

He suggested applying topical 5% imiquimod or 5-fluorouracil to identify all of the active foci by lighting up the affected areas to allow more precise surgery or ablative therapy. 

Dr. Rosen does not, however, recommend using imiquimod as primary therapy. He noted that a review of 27 published cases of 5% imiquimod for the treatment of extramammary Paget’s disease reported a 22% failure rate (Arch. Dermatol. 2011;147:704-8).

Mohs surgery shows promise for treatment of extramammary Paget’s disease, with lower recurrence rates than reported for wide surgical excision. However, experience to date with Mohs surgery for extensive disease is limited. For this reason, most authorities still consider wide surgical excision the gold standard therapy for extramammary Paget’s disease, despite published recurrence rates of 42%-54% even with clear surgical margins. Use of preoperative topical 5-fluorouracil or 5% imiquimod should substantially reduce those high recurrence rates, the dermatologist said. 

Extramammary Paget’s disease is typically slow-growing for a decade or more before invading the dermis, at which point it quickly becomes widely metastatic. 

"Once extramammary Paget’s disease has broken through the dermal/epidermal junction, it becomes a very nasty, bad-acting disease," Dr. Rosen said. 

It’s well recognized that extramammary Paget’s is associated with an increased risk of underlying internal malignancy of the lower gastrointestinal or genitourinary tract. This increased risk is typically described as being in the 10%-20% range. But that figure may be too low. A recent report from investigators at Houston’s M.D. Anderson Cancer Center involving 20 consecutive patients with extramammary Paget’s on the penis or scrotum indicated that 8 of them – fully 40% – had an associated underlying internal adenocarcinoma (J. Urol. 2011;186:97-102).

The risk of underlying internal malignancy is known to be considerably greater in white patients than in Asians. It’s very uncommon for black patients with extramammary Paget’s to have an associated internal malignancy. 

Because the full workup for an associated occult internal adenocarcinoma is elaborate and costly, a means of determining which patients are at greater or lesser risk would be welcome in order to guide the extent of testing. Cytokeratin staining may be the solution. Spanish dermatologists have reported that cutaneous extramammary Paget’s disease is characteristically positive for cytokeratin 7, negative for cytokeratin 20, and positive for cystic disease fluid protein 15. 

In contrast, endodermal extramammary Paget’s, which is more strongly associated with internal malignancy, is positive for cytokeratin 7 and 20 and negative for cystic disease fluid protein 15, according to the investigators (Clin. Exp. Dermatol. 2008;33:595-8). A cautionary note: Dr. Rosen said that to his knowledge these findings haven’t yet been confirmed by other groups. 

He reported having no financial conflicts.

SDEF and this news organization are owned by Elsevier.

YouTube Video: https://www.youtube.com/watch?v=WmMnODBDUPY