When performing a biopsy for suspected pemphigus vulgaris or mucous membrane pemphigoid, which biopsy technique is most appropriate?

For vesiculobullous diseases such as pemphigus vulgaris and mucous membrane pemphigoid, a perilesional biopsy is essential. The biopsy specimen should include tissue from the margin of the lesion (perilesional tissue) that will be sent for direct immunofluorescence (DIF) studies. Biopsying within the lesion would yield only necrotic/ulcerated tissue that is inadequate for DIF. DIF shows IgG in the intercellular spaces (pemphigus) or at the basement membrane zone (pemphigoid). A second specimen for routine histopathology may also be taken from the lesion itself.