Types and Selection Criteria for Various Skin Biopsy Procedures

The skin biopsy is a simple procedure that can assist with the diagnosis of cutaneous disorders. More errors are made from failing to biopsy promptly than from performing unnecessary biopsies. Properly performed, it may confirm a diagnosis, remove cosmetically unacceptable lesions, and provide definitive treatment for a number of skin conditions. Skin biopsies are unique because the lesion can be visualized, allowing for proper selection of biopsy site and technique. Skin biopsies can be performed with minimal risk in critically ill patients, and a timely skin biopsy may avoid other, more invasive procedures.1 Skin biopsies may be performed with shave, punch, excisional or incisional techniques. There are few absolute contraindications to skin biopsy, but all patients should be made aware that biopsies leave scars. In most cases, a biopsy should be avoided at an infected site, although occasionally ruling out infection may be the indication for the procedure. Inquiry should be made regarding allergies to topical antibiotics, antiseptics, local anesthetics, and to tape. Patients should be asked about bleeding disorders and use of drugs known to interfere with hemostasis (anticoagulants and antiplatelet agents). Generally, lesions with the most advanced inflammatory changes should be chosen; evolutionary changes may take several days and a too-early biopsy may reveal only nonspecific features.2,3, 5, 6 However for blistering diseases, the earliest lesions reveal the more specific histopathology. Consequently, only the newest vesicles and blisters should be biopsied, usually within 48 hours of their appearance.2, 3, 4 Older lesions with secondary changes such as crusts, fissures, erosions, excoriations, and ulcerations should be avoided since the primary pathological process may be obscured. For nonbullous lesions, the biopsy should include maximal lesional skin and minimal normal skin. For lesions between < 4 mm in diameter, the central region should be biopsied or the entire lesion be excised. For larger lesions, the edge, the thickest portion, or the area with abnormal coloration should be biopsied, because these sites will most likely contain the distinctive pathology. Vesicles should preferably be biopsied intact with adjacent normal-appearing skin, because disruption makes histological interpretation more difficult. Similarly, bullae should be biopsied at their edge, keeping the blister roof attached. If the differential diagnosis is broad, taking biopsy from several sites can minimize sampling error. Important cosmetic areas, such as the face should be approached with caution, and areas with poor healing characteristics should be avoided if other sites are available for biopsy.4, 6 Hypertrophic scarring tends to occur over the deltoid and chest areas, and delayed healing can be a problem over the tibia, especially in diabetic patients or in patients with arterial or venous insufficiency.6 The