DISCUSSION
The next step in this patient's evaluation was a punch biopsy because it could provide the essential element that is missing in many such cases: a correct diagnosis.
Troublesome possibilities The differential diagnosis for progressive and unresponsive groin rashes demands biopsy because it includes some rather serious, albeit unusual possibilities. The results of this patient's punch biopsy were consistent with extramammary Paget's disease (EMPD). In most cases, EMPD represents a type of primary cutaneous adenocarcinoma in which there is epidermal infiltration of neoplastic cells of glandular differentiation, typically apocrine in origin. EMPD is histologically and morphologically identical to mammary Paget's disease, although the latter is almost always indicative of an underlying intraductal carcinoma of the breast. EMPD can spread to deeper structures and can even metastasize. It can also be related to other underlying malignancies, such as perianal EMPD, which is associated with colorectal carcinoma in 25% to 35% of cases, as well as with prostate or bladder cancer. The differential diagnosis for EMPD also includes cutaneous T-cell lymphoma, lichen simplex chronicus, psoriasis, superficial basal cell carcinoma, and Bowen's disease, in addition to the infectious etiologies that were ruled out by failure to respond to antiyeast and antifungal therapy.
Getting to the diagnosis Given the failure of previous treatment, infection of any kind was unlikely, so culture would not be worthwhile. Gentian violet can sometimes be helpful for difficult cases of intertrigo, but in this case, an accurate diagnosis was deemed to be the more pressing need. Finally, treating with oral imidazoles, such as fluconazole (Diflucan, generics), was not only unlikely to help but also ignored the need for a specific diagnosis.
Outcome This patient had no associated internal malignancy. As of this writing, he was being treated with imiquimod (Aldara) cream. This medication has proved to be an effective alternative to the draconian surgical procedures that are still considered the gold standard for EMPD. Other treatments include topical chemotherapy, such as 5-fluorouracil cream. JAAPA
Joe Monroe practices at the Dawkins Dermatology Clinic, Oklahoma City, Oklahoma, and is the department editor for Dermatology Digest. He has indicated no relationships to disclose relating to the content of this article.