Which instrument is used to obtain a full-thickness punch biopsy typically 2-8 mm in diameter (mostly 4 mm)?

• A. Scalpel
• B. Punch biopsy
• C. Curette
• D. Needle biopsy

Answer: (B)

The instrument being tested is designed to obtain a full-thickness cylindrical skin sample. It has a circular blade at the end of a hollow handle. By pressing the blade into the skin and twisting, it cores out a plug that includes epidermis and dermis (and sometimes shallow subcutaneous fat), producing a cylindrical specimen. Sizes range from about 2 to 8 mm in diameter, with 4 mm being the most commonly used in practice, because it provides enough tissue for histology while keeping the wound manageable. After removal, the specimen is retrieved with forceps and the resulting wound can be closed with sutures or left to heal by secondary intention, depending on size and location. Other instruments don’t yield this kind of cylindrical, full-thickness sample: a scalpel makes incisions, a curette scrapes, and a needle biopsy collects a different, typically smaller sample.