Failure of Extensive Extramammary Paget Disease of the Inguinal Area to Clear With Imiquimod Cream, 5%

Background  Surgical approaches are the standard treatment for extramammary Paget disease (EMPD), but nonsurgical modalities may be preferred and more appropriate for some patients. Topical administration of imiquimod cream, 5%, has improved or resolved in situ EMPD (n = 21), but treatment failures (n = 6) have also been reported.

Observations  We treated an elderly patient with initial biopsy-proved in situ genital EMPD with daily topical imiquimod, 5%, for 14 weeks. Midtreatment mapping biopsy specimens demonstrated invasive disease, with minimal clinical improvement. The patient subsequently underwent surgical excision.

Conclusions  Of the 27 published cases that describe imiquimod treatment of EMPD, 6 report treatment failure (22%), but factors that may contribute to treatment failure are not well understood. In the present patient, treatment with imiquimod may have been complicated by variable lesion thickness, which inhibited uniform penetration of imiquimod, or the presence of invasive disease not detected on initial biopsy. The efficacy of imiquimod to treat extensive invasive EMPD has not been demonstrated, and surgical approaches remain the most appropriate treatment for invasive disease. Variable responses to topical imiquimod use among patients suggest that other factors may be important in determining response to therapy.

Surgical management of extramammary Paget disease (EMPD) remains a therapeutic mainstay, but alternative treatments for primary limited cutaneous EMPD in the anogenital area that avoid cosmetic and functional defects after extensive tissue removal are under investigation. Local recurrence of EMPD can be significant,1 highlighting the insidious nature of EMPD and the need to identify more effective treatments. The topical immunomodulator imiquimod, 5%, has been reported to induce clinical and histologic resolution of superficial EMPD,212 but several cases of imiquimod failure have also been described.1317 Herein, we present a case of genital EMPD considered to be limited to in situ disease at the beginning of treatment with topical imiquimod that proved refractory, with demonstration of invasive disease during treatment. We also review the current literature (articles published in English and obtained through PubMed, Ovid, and GoogleScholar searches conducted between July 1, 2009, and August 31, 2010) regarding successes (n = 21) and failures (n = 6) of imiquimod therapy for EMPD and present characteristics that could portend treatment failure.