Evaluation of mapping biopsies for extramammary Paget disease: A retrospective study

Background: Extramammary Paget disease (EMPD) sometimes shows an ill-defined border and an unexpectedly extended tumor spread beyond the clinical borders. Mapping biopsy is 1 approach for complete surgical removal, but its efficacy has remained controversial. Objective: We sought to evaluate mapping biopsies for EMPD. Methods: We performed a retrospective review of 133 patients with 150 primary EMPD lesions. We histopathologically examined 1182 skin biopsy specimens (975 from mapping biopsy and 207 from lesional biopsy). Results: Only 1.6% of mapping biopsy specimens from well-defined EMPD (13 of 810) were positive. Moreover, 4.6% of mapping biopsy specimens from ill-defined EMPD (8 of 165) were positive, whereas all specimens taken from sites 2 cm or more from the clinical border were negative. For both well-defined and ill-defined EMPD, there was no significant difference in the margin status of surgical resection regardless of mapping biopsy. Limitations: This was a retrospective study. Conclusions: Mapping biopsies are unnecessary for well-defined EMPD or when 2-cm margins can be achieved, whereas surgical removal with predetermined margins (1 cm for well-defined EMPD and 2 cm for ill-defined EMPD) appears to be safe. Mapping biopsies can be considered when shortening of the safe surgical margin to less than 2 cm is required in ill-defined EMPD.