Skin is uniquely available for diagnostic procedures as well as for the direct application of therapeutic agents. This ease of access allows multiple procedures to be performed in a short period with little discomfort to the patient. Most techniques are easily learned and require only simple equipment.

The punch biopsy is an easily learned procedure that, in all but a very few circumstances, removes sufficient tissue for histopathologic study. The information derived from this procedure is important not only for diagnostic purposes but also to clarify a disease process and to assess the extent of tissue involved, because full-thickness tissue is usually obtained.

1. Selecting Biopsy Site. It is generally best to select a mature, welldeveloped, untreated lesion for biopsy. If vesicles or bullae are present, choose the earliest lesion available, and take care to keep the roof intact. The clinician should intentionally include adjacent normal skin. Several biopsies should be obtained from evolving eruptions or those with various types of lesions (in this instance, too, biopsy of early lesions may be of higher diagnostic yield). Lesions altered by trauma or prior treatment or “burned-out” areas will not yield useful information. It should be noted that biopsies on the legs and feet heal more slowly than proximal biopsies, especially if the circulation is poor. Therefore, if possible, choose a lesion above the knees. Choose a site entirely within the lesion. Avoid including normal skin in the biopsy unless specifically desired, in which case the pathologist should be informed of its inclusion and how the specimen is oriented.

2. Pre-anesthesia. Clean the area gently with alcohol, taking care to leave scales, crusts, and vesicles intact. It is often useful to outline small lesions before the injection of local anesthetic, because the effect of epinephrine distorts and blanches the site.

3. Anesthesia. Anesthetize the area by injecting into the deep dermis 0.2 to 0.5 mL of 0.5% to 2.0% lidocaine or 1% to 2% lidocaine with 1:100,000 epinephrine. Addition of sodium bicarbonate to the lidocaine (approximately one part of 8.4% sodium bicarbonate to nine parts of 2% lidocaine) will attenuate the burning sensation during infiltration. Patients allergic to local anesthetic ether compounds (procaine and tetracaine) can tolerate amide compounds (lidocaine and bupivacaine) without difficulty. For example, procaine (Novocaine) and lidocaine (Xylocaine) do not cross-react. Other alternatives for delivering local anesthesia include antihistamines such as diphenhydramine HCl or normal saline
with preservative. The local vasoconstriction produced by epinephrine will diminish bleeding and prolong the duration of anesthesia, thereby making the procedure easier to perform. For maximal vasoconstriction, a delay of 15 to 20 minutes post-injection is required. Epinephrinecontaining solutions should be used with caution when vasoconstriction might interfere with the histopathologic findings (i.e., vascular lesions). Although some surgeons prefer to ring block an area with anesthesia, intradermal injection directly into or below a lesion appears to cause little or no perceptible microscopic alteration. Epinephrine-containing solutions are also used with caution when anesthetizing acral areas such as the penis, earlobes, and distal fingers or toes. However, more recent studies have indicated that there is likely no increased risk of ischemia or necrosis when using epinephrine-containing anesthetics in these areas, despite a history of circulatory disorders, thrombosis, diabetes, smoking, anticoagulation, or significant preoperative hypertension.¹ For larger excisions, patients with severe diabetic angiopathy, Raynaud disease, or those receiving monoamine oxidase inhibitors or β-blockers should not receive vasoconstrictors.

To minimize trauma for the patient, a 30- or 32-gauge needle should be used. The pain of needle insertion is reduced by reassurance, verbal distraction, quick placement, slow diffusion, and mechanical distraction, such as pinching or vibration immediately proximal to the injection site.² A topical anesthetic cream may be used to dull the pain of injection in children or for larger excisions. Topical anesthetics typically must be applied at least 1 hour before the procedure for maximal effects. Use of occlusion enhances the numbing effects. Using buffered anesthetic that is warmed to body temperature will help reduce the stinging sensation during injection.

4. Instrument Choice. Punch biopsy instruments have a cylindrical sharp cutting tip and a handle and are available in sizes ranging from 1 to 8 mm in diameter. The 4-mm punch is generally the most useful. About 6- to 8-mm punch biopsies tend to leave standing cone “dog ear” deformities at the edges, thereby needing subsequent wound repair. Removal of a specimen <4 mm in diameter may allow the histologic confirmation of a tumor, but is often inadequate for diagnosis of inflammatory processes.

5. Punch Technique. The skin surrounding the lesion should be stretched taut perpendicular to the wrinkle (relaxed skin tension) lines before the circular punch is inserted vertically, as demonstrated in Figure 48-1. When the punch is removed, an ellipsoidal defect will be left (Fig. 48-1, insets). The biopsy punch is pressed firmly downward into the lesion with a rotary cutting motion in one direction until it is well into the subcutaneous tissue (Fig. 48-1). If the incision is made only to mid-dermis, the tissue will be more difficult to remove and the wound will heal less rapidly and with a less satisfactory cosmetic result. Care should be taken to avoid underlying structures when visible (e.g., visible vessel, tendons), especially in areas with thinner skin.

The biopsied skin plug will either pop up or lie free within its circular margin. The specimen must be grasped gently and lifted out with a forceps without applying undue pressure. The base must be severed with a scissors or scalpel blade as deep into the fat as possible, and the tissue placed in 10% neutral
buffered formalin. The amount of formalin should be at least 20 times that of the specimen by volume. To avoid an artificial split in the skin, grasp the specimen close to the base with the forceps.

Simple pressure is generally adequate for hemostasis. Rarely, 20% aluminum in ethyl alcohol (e.g., Drysol), ferric subsulfate (Monsel solution), absorbable gelatin (Gel foam), or electrodesiccation may be needed. Ferric subsulfate may occasionally result in pigmented tattoos and may destroy more tissue than other methods. Lesions heal more rapidly and with a linear scar if they are closed with appropriate sutures and not left as a round defect (sutures are left for 5 to 7 days on the face or 10 to 14 days on the trunk). Adhesive strips may also be applied across the defect (left for 14 to 21 days). If the patient cannot return for suture removal, an absorbable suture can be used to close the punch biopsy site.

The histologic interpretation of cutaneous reaction patterns requires a great deal of judgment and experience. It is wise to seek the help of a dermatopathologist. A clinical pathologic correlation should be made and follow-up consultation or a second opinion requested if there are questions regarding the diagnosis, especially of a pigmented lesion.

A shave biopsy allows the easy removal of epidermal and papillary dermal tissue for histopathologic inspection. It removes that portion of skin elevated above the plane of surrounding tissue and is useful for biopsying or removing many exophytic benign epidermal growths, including keratoses and viral tumors. Shave biopsies are most useful for obtaining
a tissue diagnosis of malignant lesions such as basal cell and squamous cell carcinomas. This procedure is quickly and easily performed, heals rapidly, and yields a good cosmetic result. In addition, it leaves the lower levels of the dermis intact if further procedures such as curettage, electrosurgery, and cryosurgery are necessary. The decision to perform a shave biopsy requires some judgment and, in particular, a reasonably good impression of the preoperative diagnosis. A shave biopsy may fail to distinguish, for example, between an actinic keratosis and an invasive squamous cell carcinoma if the shave is too superficial. It is controversial to perform a shave biopsy for melanoma diagnosis since it may fail to obtain the entire depth of lesion. Finally, this technique typically is not preferred for diagnosing inflammatory lesions.

A. Pre-biopsy Preparation. Clean and anesthetize the area as noted above for punch biopsy.

B. If a Substantial Margin of Tissue Surrounding and Below the Lesion Is Needed,

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