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Extramammary Paget’s disease (EMPD) is a rare adenocarcinoma which usually presents as an enlarging erythematous plaque on anogenital skin of the elderly. It can grow slowly and is often misdiagnosed clinically as a dermatosis for years before a biopsy discovers the correct diagnosis.
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EMPD infiltrates the epidermis and spreads radially as unpredictable frond-like extensions extending far beyond what is perceived clinically. Metastatic disease from adnenocarcoma of other sites (usually colorectal or prostatic) can infiltrate the epidermis and precisely mimic EMPD histopathologically. This possibility needs to be considered before surgical management is discussed.
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Margin control surgery (MCS) is an appealing option for these tumors due to the frequent significant subclinical spread. Review of case reports comparing those treated with conventional surgery versus MCS shows of 2.5-fold higher risk of recurrence with conventional surgery.1 Other reports have shown a recurrence rate of 23% for MCS versus 33% for conventional surgery.2
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MULTIDISCIPLINARY APPROACH
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Cases are usually presented at a multidisciplinary meeting (MDM) to discuss the diagnosis and therapeutic options. A typical scenario would be a protracted clinical course (before the diagnosis is made) and multiple unsuccessful attempts to achieve a clear surgical margin with wide local excision (WLE). Topical or destructive therapeutic options are also often considered, especially for larger lesions. Input from dermatology as well as gynecological, urological, colorectal, and plastic/reconstructive surgeons is typically sought. The pathology is usually reviewed to confirm the diagnosis and radiology may be reviewed to further exclude the possibility of disease metastatic from an internal primary adenocarcinoma.
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Radical resection often means complete vulvectomy or penectomy and without MCS these may still result in positive surgical margins. Though cases of multifocality have been described, there is mounting evidence that this is rare, if it occurs at all.3,4
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Due to the large size of these tumors, a modified approach is often used with a complete peripheral margin assessment performed under local anesthetic (with the central tumor left intact) followed by the excision of the central tumor under general anesthetic. Sometimes the tumor is so ill-defined that it is not clear where the excision of the first level should be performed. In these cases, scouting biopsies may be used to help roughly determine the extent of disease. Biopsies that sample the maximum amount of epidermis (e.g., broad-shave biopsies) are preferred. Reflectance confocal microscopy may also help in the delineation.5 The radial margin is removed as a thin strip, mapped, and embedded en face for examination of the entire margin. This is sometimes called the “spaghetti” technique6 (Fig. 14.1).
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