Extramammary Paget's disease (EMPD) is an intraepithelial carcinoma usually occurring on the skin or mucosa of the perineum. Clinically, it resembles eczema or dermatitis, and misdiagnosis and treatment delays are common. The treatment of choice for EMPD is a wide excision with adequate margins. Wide excision with intraoperative frozen biopsy and Mohs micrographic surgery are common methods; however, these are associated with a high recurrence rate and long operation time, respectively.

Between January 2010 and June 2013, 21 patients diagnosed with EMPD underwent mapping biopsy. Biopsy specimens were collected from at least 10 areas, 2 cm from the tumor margin. When the specimens were positive for malignancy, additional mapping biopsy was performed around the biopsy site of the positive result, and continued until no cancer cells were found. Based on the results, excision margins and reconstruction plans were established preoperatively.

The patients (18 male, 3 female) had a mean age of 66.5 years (range, 50-82 years). Almost all cases involved in the perineal area, except one case of axillary involvement. Permanent biopsy revealed one case (4.8%) of positive cancer cells on the resection margin, in which additional mapping biopsy and re-operation was performed. At the latest follow-up (mean, 27.4 months; range, 12-53 months), recurrence had not occurred.

Preoperative mapping biopsy enables accurate resection margins and a preoperative reconstructing plan. Additionally, it reduces the operation time and risk of recurrence. Accordingly, it represents an effective alternative to Mohs micrographic surgery and wide excision with intraoperative frozen biopsy.