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Skin biopsy techniques

Skin biopsy techniques
Authors:
Patrick C Alguire, MD, FACP
Barbara M Mathes, MD, FACP, FAAD
Section Editors:
Russell S Berman, MD
Stanley J Miller, MD
Deputy Editor:
Rosamaria Corona, MD, DSc
Literature review current through: Jul 2022. | This topic last updated: May 10, 2021.

INTRODUCTION — The skin biopsy is a relatively simple but essential procedure in the management of skin disorders [1]. The most commonly performed biopsy procedures are reviewed here. Biopsy of the nail apparatus is discussed separately. (See "Nail biopsy: Indications and techniques".)

INDICATIONS — More errors are made from failing to biopsy promptly than from performing unnecessary biopsies. Nevertheless, many dermatoses have nonspecific histopathology, and biopsy cannot substitute for good clinical skills [2-4]. Biopsy is indicated in the following circumstances (table 1) [2,4,5]:

All suspected neoplastic lesions

All bullous disorders

To clarify a diagnosis when a limited number of entities are under consideration

Biopsy can also serve as the definitive treatment for irritated, inflamed, precancerous, or malignant lesions [2,4-6]. However, for malignant lesions, a pathologic report indicating that the biopsy margins are "clear" does not necessarily mean that there has been adequate therapy. (See "Epidemiology, pathogenesis, and clinical features of basal cell carcinoma" and "Cutaneous squamous cell carcinoma (cSCC): Clinical features and diagnosis".)

CONTRAINDICATIONS — There are few absolute contraindications to skin biopsy. It usually should not be performed at an infected site, although occasionally infection is the indication for the procedure.

PREPROCEDURE CONSIDERATIONS — Prior to proceeding to a skin biopsy, patients should be asked about allergies to topical antibiotics, antiseptics, local anesthetics, and reactions to tape.

Inquiries should also be made regarding bleeding disorders, bleeding with previous surgery, and use of drugs known to interfere with hemostasis. (See "Preoperative assessment of hemostasis".)

Excessive bleeding is rarely a problem in patients taking oral anticoagulants or antiplatelet agents. Patients taking aspirin can generally be managed with careful attention to hemostasis and the use of a pressure dressing (see 'Hemostasis' below and 'Complications' below). We suggest that patients on oral anticoagulants or antiplatelet agents be referred to a dermatologist or surgeon for biopsies. These medications should generally not be discontinued for simple skin biopsies. We also suggest referral to a dermatologist or surgeon for biopsies in patients with bleeding disorders. (See "Skin surgery: Prevention and treatment of complications", section on 'Patients on anticoagulants and antiplatelet agents'.)

SITE SELECTION — Site selection can be critical to diagnosis. The appropriate biopsy site depends upon the type of lesion:

For inflammatory lesions, those with characteristic inflammatory changes (eg, erythema) should be biopsied first; evolutionary changes may take time so biopsies performed too early and very late lesions may reveal only nonspecific or secondary features [2-4,7-9].

For blistering diseases, early evolving lesions have more specific histopathology and are preferred for biopsy. Only the newest vesicles and blisters should be biopsied, ideally within 48 hours of their appearance. Older lesions with secondary changes such as crusts, fissures, erosions, excoriations, and ulcerations should be avoided since the primary pathologic process may be obscured. (See "Approach to the patient with cutaneous blisters", section on 'Skin biopsy'.)

The location of biopsy within a particular lesion also depends upon the type and size of the lesions:

For nonbullous lesions, the biopsy should include maximal lesional skin and minimal normal skin. For lesions between 1 and 4 mm in diameter, biopsy the center or excise the entire lesion. For large lesions, biopsy the edge, the thickest portion, or the area that is most abnormal in color; these sites will most likely contain the distinctive pathology.

When vesicles are biopsied, remove vesicles intact when possible, with adjacent normal appearing skin; disruption makes histologic interpretation more difficult.

Bullae should be biopsied at the edge to include a small part of the blister with adjacent intact skin, keeping the blister roof attached. This technique is important for diagnosis; it allows the pathologist to determine the level of blister formation within the skin (eg, subcorneal, intraepidermal, subepidermal). (See "Approach to the patient with cutaneous blisters", section on 'Skin biopsy'.)

Several sites should be biopsied if the differential diagnosis is broad to minimize sampling error.

Important cosmetic areas such as the face and areas with poor healing characteristics (distal lower extremities) should be avoided if possible when choosing a biopsy site for a generalized process [4,8,10]. When there are individual suspicious lesions involving the face or other cosmetically important areas, it may be preferable to refer the patient to a dermatologist or plastic surgeon who has expertise in such biopsies.

All biopsies leave scars. Hypertrophic scarring tends to occur over the deltoid and chest areas; delayed healing can be a problem over the tibia, especially in patients with diabetes or in patients with arterial or venous insufficiency [8]. The incidence of secondary infection in the groin and axillae is high; biopsy these areas only if other sites are unavailable [3].

BIOPSY TECHNIQUES

General measures — Shave and punch biopsies are clean, not sterile procedures; mask, gown, and sterile gloves are not necessary [7,11]. Mask, gown, and sterile gloves are indicated for excisions and are reasonable for any patient at increased risk of infection [7]. A list of the supplies and instruments necessary is shown in the table (table 2).

Biopsy site identification — It is important to identify the biopsy site before performing the definitive surgical treatment to avoid wrong-site surgery [12]. Several methods have been used for the identification of the biopsy site, including reporting in medical records the accurate description of the lesion and surrounding anatomic landmarks and/or measurements from at least two fixed landmarks, marking the site with tattoo ink, and taking a photograph of the biopsy site. There is consensus among experts that taking a high-quality photograph of the lesion that includes one or more visible anatomic landmarks at the time of biopsy provides a quick and unequivocal documentation of the biopsy site [13].

Preparing the site — Any common skin antiseptic such as isopropyl alcohol, povidone-iodine, or chlorhexidine gluconate can be used to prepare the biopsy site [3,5,7]. Mark the intended lesion with a surgical marker since it may be temporarily obliterated following injection of the anesthetic. Marking the outlines for excisional biopsies also can be helpful. For excisions, place a fenestrated surgical drape over the biopsy site after the area is cleansed and anesthetized.

Round wounds tend to be pulled open in the direction of skin tension lines (known as Langer's lines) that generally parallel the direction of collagen in the dermis [10,14,15]. Tension lines can be demonstrated by gently compressing relaxed skin with the thumb and index finger; wrinkle lines on the face are another good indicator. Surgical incisions placed parallel to tension lines will close more easily and cosmetically than those placed at right angles (picture 1) [6,10,14,15].

Anesthesia — The most commonly used local anesthetic is 1 or 2% lidocaine. The combination of lidocaine and epinephrine (eg, lidocaine hydrochloride 1% or 2% and epinephrine 1:100,000) has several advantages over lidocaine alone: blood vessel constriction, decreased bleeding, prolonged anesthesia, and reduced lidocaine toxicity [5,16]. The onset of vasoconstriction is about 10 minutes slower than that of anesthesia.

Given the vasoconstrictive properties of epinephrine, concern has been raised regarding the possibility of epinephrine-induced ischemic necrosis in areas such as the digits, ears, and nose [6,10,16]. However, the results of some studies suggest that with proper technique, local infiltrative anesthesia with dilute solutions of lidocaine with epinephrine may be safe for use in these areas [17-20].

The following can minimize the sting of injection [3,5,14]:

Mix 1 mL of sodium bicarbonate 1 mEq/mL with 9 mL of lidocaine.

Use a 30-gauge needle.

Make the initial injection perpendicular (or near perpendicular) to the skin.

Deep injections sting less than superficial injections but prolong the time to adequate anesthesia [3].

Small syringes (1 and 3 cc) permit easier injections and are less cumbersome to handle.

The anesthetic can be injected directly into or immediately adjacent to small lesions. The anesthetic must be infiltrated into the dermis if it is being used to elevate a lesion for biopsy. A field block should be performed for larger lesions by placing a ring of anesthetic around the surgical site, advancing and injecting through a site that has been previously anesthetized [14,21]. (See "Subcutaneous infiltration of local anesthetics".)

Choice of procedure — Shave biopsies can be done in a short amount of time, require minimal training, and do not require sutures for closure; a small depressed scar about the size of the initial lesion is likely to occur [22]. Lesions that are most suitable for shave biopsies are either elevated above the skin surface or have pathology confined to the epidermis [5,7,14,22]. Examples include seborrheic or actinic keratoses, skin tags, warts, and superficial basal cell or squamous cell carcinomas. Superficial shave biopsies should not be used for pigmented lesions; an unsuspected melanoma cannot be properly staged if partially removed [4,5,7,23]. (See 'Biopsy of pigmented lesions' below.)

Punch biopsies are performed with round, disposable knives ranging in diameter from 2 to 10 mm; 3 mm is the smallest size likely to give sufficient tissue for consistently accurate histologic diagnosis [24]. The punch is an ideal procedure for diagnostic skin biopsy or removing small lesions. It often provides a better cosmetic result than a shave biopsy [3,7,22]. Punch biopsies are easily mastered by most practitioners, are quick, and have a low incidence of infection, bleeding, nonhealing, or significant scarring [3,7,22]. They can heal by secondary intention, but punches greater than 3 mm may produce unacceptable scarring and are best closed with one or two sutures.

Excisions are performed for lesions that require complete removal for diagnostic or therapeutic purposes and for lesions that cannot be adequately biopsied with a punch due to size, depth, or location. An excisional biopsy allows for histopathologic examination of an entire lesion. Another advantage of an excisional biopsy is the amount of tissue that can be excised, allowing for multiple studies (culture, histopathology, immunofluorescence, electron microscopy) from one biopsy site [3,7]. Excisions are especially well suited for removal of large skin tumors or inflammatory disorders deep in the skin involving the panniculus.

Excisions require the greatest amount of expertise and time; they almost always require sutures, and are more easily performed with an assistant [3,7]. We recommend that practitioners receive clinical training before attempting an excisional biopsy, or refer patients requiring an excision to a qualified dermatologist or surgeon.

Shave biopsy — Shave biopsies can be either superficial or deep. Superficial shave biopsies are done across or nearly parallel to the skin surface and extend into the epidermis only or epidermis and limited superficial dermis (figure 1).

The shave biopsy can be facilitated by raising the lesion with a wheal of injected anesthetic, allowing the lesion to be propped up and stabilized between the thumb and forefinger (figure 2) [6,10,22].

When performing a superficial shave biopsy, a number 15 blade on a scalpel is held tangential to the skin surface. The lesion is then removed with a forward smooth sweeping stroke of the blade going just under and across the lesion (figure 2).

The deeper shave biopsy allows for sampling of dermis and epidermis (figure 1), important for assessing basal cell and squamous cell carcinomas (superficial shave biopsies of exophytic tumors may only contain epidermal tissue, preventing histologic differentiation between in situ and invasive malignancy). For this biopsy, the clinician holds the scalpel like a pencil, makes a small vertical incision into the skin with the beveled tip of the number 15 scalpel blade, then turns the scalpel and moves the blade forward in a horizontal sawing motion, turning the blade up towards the surface to finish the excision [9]. The defect created is that of a saucer (hence the alternative name "saucerization" biopsy).

In both biopsies, the index finger can be placed on top of the lesion near the end of the excision to stabilize and prevent tearing. Since the angle of the blade controls the depth of the biopsy, attention should be paid to the angle entering and exiting the skin.

A double-edge razor blade cut longitudinally also can be used for shave biopsies (picture 2). The razor technique has several advantages:

The razor is sharper than most surgical blades.

The razor can be bent concave or convex with the thumb and forefinger to better conform to the surface being cut.

Depth is easily controlled by increasing or decreasing the convexity of the curve.

Devices are available that provide a holder or handle for the razor blade and many clinicians find these helpful.

Curved scissors are an efficient means of removing skin tags and other small exophytic growths [5]. The lesion to be removed is stabilized with toothed forceps, then cut at the base.

Hemostasis — Bleeding following small shave biopsies can often be controlled with pressure alone. Persistent oozing may be stopped with 10 to 20% aluminum chloride in absolute alcohol (eg, aluminum chloride hexahydrate). Other hemostatic agents, in order of increasing corrosiveness, are Monsel's solution (ferric subsulfate), trichloroacetic acid, and silver nitrate [25]. Monsel's solution is more effective than aluminum chloride, but also causes more tissue destruction and, like silver nitrate, can result in skin pigmentation (permanent tattoos).

The wound must be as dry as possible for hemostatic agents to be effective. The agent is applied with a cotton applicator using firm pressure with a twisting motion [14]. Excellent hemostasis generally can be achieved in patients with bleeding disorders or in those taking oral anticoagulants or antiplatelet agents with the combined use of aluminum chloride and several minutes of direct pressure over the wound.

Punch biopsy — Punch biopsies are relatively simple and the specimen is a cone shaped core of tissue with its widest diameter at the skin surface and narrowest at the biopsy base. The direction of the skin tension lines at the biopsy site should be determined prior to performing a punch biopsy. Raise an intradermal welt (wheal) with the anesthetic and select the appropriate size punch. Stabilize the skin with the thumb and forefinger, stretching it slightly perpendicular to the normal skin tension lines; this will produce an oval rather than round wound, facilitating closure [4-6]. Place the punch perpendicular to the skin and apply firm and constant downward pressure with a circular twisting motion (picture 3). Avoid removing the punch to "check the progress;" this may result in a ragged wound and a shredded biopsy sample [14,22].

A definite "give" occurs when the punch reaches the subcutaneous fat, indicating that a full-thickness cut has been made. Remove the punch and apply downward finger pressure at the sides of the wound to pop up the core. Completely elevate the core with gentle use of forceps or a needle tip and excise it at its base with small tissue scissors. Apply pressure to the wound with gauze in preparation for closure.

Punch biopsies of the scalp for diagnosis of hair disorders are best accomplished using a 4 mm punch and holding it at 20° to the surface of the scalp, roughly along the axis of the hair follicle [7,26]. Biopsies of scalp lesions suspected of being malignant are performed in the same manner as other punch biopsies, with the punch perpendicular to the skin surface. Scalp biopsies bleed profusely and usually require the presence of an assistant [26].

Punch biopsies can be closed with one or two sutures or allowed to heal by secondary intention. A randomized trial in volunteers found that the results with secondary intention healing after 4 mm punch biopsies were at least as good as with suturing, but that patients preferred the appearance of 8 mm punch biopsies that were sutured [27].

Wounds that are allowed to heal by secondary intention may be treated with a hemostatic agent such as aluminum chloride or absorbable gelatin; do not apply a hemostatic agent if sutures are to be used. Contraindications to suturing include biopsies in infected or poorly healing skin; these wounds heal better by secondary intention [7].

Excision — The direction of the skin tension lines should be determined after performing a field block in preparation for an excision. Align the long axis of the excision parallel to the skin tension lines (picture 1). Using a surgical marking pen, draw an ellipse around the lesion to be excised, including a 2 to 5 mm margin of normal skin around the lesion, with 30° angles at each apex, and the length three times the width (figure 3) [5,6]. Holding the scalpel with a number 15 blade like a pencil, begin the incision at one apex with the blade perpendicular to the skin. As the incision progresses, use more of the belly of the blade, raising it to the perpendicular again at the next apex [6]. (See "Fusiform/elliptical excision".)

The blade should be angled away from the lesion, slightly undermining the wound edge. This will allow for easier eversion of the wound edge during closure, improving the cosmetic result and decreasing the risk of dehiscence. Avoid crosshatching the incisions at the apices and nicking the sample. It is not necessary to go through the entire thickness of dermis on the first stroke, although ultimately the incision must extend completely through the dermis and be deep enough to see subcutaneous fat when the sample is removed.

Carefully lift the sample edge with fine forceps once the ellipse has been incised and completely undermine the sample at the level of the subcutaneous fat with scalpel or scissors. Do not remove more tissue at the center than at the apices. Apply pressure to the wound with gauze in preparation for closing.

It may be technically easier to perform a diamond-shaped excision for small lesions and a hexagonal-shaped excision for larger lesions [4]. For diamond excisions, the blade is inserted vertically into the skin to make the four straight-line incisions of the diamond. For the hexagon, two straight, parallel lines are incised on either side of the lesion and then connected at each end by two more straight incisions to form the hexagon.

The edges of the wound may need to be undermined prior to closing excisional wounds, either sharply with a scalpel or bluntly with scissors. Blunt dissection is performed by advancing the closed scissors under the wound edge at the dermal-subcutaneous junction, and quickly spreading them open. The width of undermining varies with the size of the wound; for most wounds 5 to 10 mm is sufficient. Undermining allows the skin edges to evert more easily and reduces tension on the sutures [3,6,7,14,21].

Processing the biopsy sample — For evaluation by light microscopy, the specimen should be placed in a 10% buffered formalin solution; each specimen is placed into a separate bottle and identified. Specimens less than 1 cm in greatest dimension can be adequately fixed in 30 mL of formalin; larger specimens require more formalin and should be sectioned to ensure adequate fixation. The pathologist should be informed if the specimen is sectioned and advised of the orientation of the lesion by sectioning through its center and marking the normal skin borders with a surgical marker.

Special studies require special handling [1]:

Direct immunofluorescence – Michel's buffered solution

Electron microscopy – glutaraldehyde buffered solution

Bacterial or fungal cultures – sterile container with nonbacteriostatic saline

Viral cultures – viral transport media

Pathology requisition information — Since many dermatologic diagnoses are predicated upon clinicopathologic correlation, the skin biopsy requisition form should include adequate information regarding the patient and the lesion or process biopsied, including the patient's demographics and relevant medical history, clinical appearance, size, and location of the lesion, clinical course, and previous treatments [28].

Suturing — Primary closure of a punch wound can be accomplished with one or two, single-layer, interrupted sutures. Some punch wounds can be allowed to heal by secondary intention. (See 'Punch biopsy' above.)

Excisions can be closed in one or two layers; two-layer closures yield better cosmetic results for larger wounds.

Choice of suture and needle — The qualities most important in suture are flexibility, strength, secure knotting, and infection potential [29]. The two major categories of suture are absorbable and nonabsorbable. Absorbable suture is made from synthetic polymer or mammalian-derived collagen (gut). Common synthetic absorbables include polyglactic acid (Vicryl), polyglycolic acid, and polydioxanone (PDS). Absorbable sutures are usually placed deep in larger wounds to reduce skin tension for the final closure. (See "Skin laceration repair with sutures".)

Nonabsorbable sutures are used for skin closure and permanent internal placement, such as cardiac valves. Common nonabsorbable sutures include silk, nylon, and polypropylene (Prolene). Silk and nylon sutures can be braided, adding strength and improving knotting potential, but they are more likely to harbor infection. Polypropylene and unbraided nylon are monofilaments and are less likely to harbor infection, but knots are less secure and more difficult to tie [10,29]. Polypropylene should be considered for the scalp, primarily because it is blue and easy to see. Silk and gut, as natural materials, cause considerable tissue inflammation and have been largely replaced by synthetic suture material [10,29].

Suture size is indicated by the code O: the more O's, the smaller the suture diameter. Generally, 4-O or 5-O monofilament nylon can be used on the body and scalp, and 6-O nylon on the face [6,14].

Suture needles are made of noncorrosive stainless steel that is forged to achieve maximum strength and ductility, the ability to bend under pressure without breaking [29]. Three types of needle points are common: cutting; tapered; and blunt. Cutting needles allow for easy passage through tough tissue and are ideal for skin.

A code has been developed to denote the purpose of the needle. For skin (FS) and cutting needles (CE) are used on thick skin, while plastic (P), plastic skin (PS), and premium (PRE) are used for cosmetic closures. The size of the needle is ranked by a number, with higher numbers identifying larger needles. Needle curvature is measured in terms of proportion of a circle, with one-quarter, one-half, and three-eighths curves available.

Most biopsy wounds in thick skin can be closed using an FS-3 or CE-3 needle; P-3 can be used for the face, all with a three-eighths curvature. C-17 needles were developed specifically to close punch biopsies and are less expensive than FS, CE, P, or PRE needles.

Reassess the appropriateness of the instruments when wound closing seems more difficult than expected. Needle selection is often a prime factor determining the ease of suturing and final cosmetic result [21]. A larger needle may decrease the difficulty of the job.

Closing — The most common closure technique is a simple, interrupted suture [14]:

To begin, grasp the needle with the needle-holder at midpoint or about one-third the distance from the eye. This will provide maximum driving force and diminish the likelihood of bending or breaking the needle. A palm grip is recommended to increase the driving force of the needle through the skin. Place the handle of the holder in the palm, wrap the thumb and fingers around the handles, and extend the index finger down over the tip of the holder near the needle.

The needle point is placed perpendicular to the skin surface about 2 mm away from the wound edge and is driven down, then up into the center of the wound. A second insertion begins in the center of the wound and exits the skin on the opposite side, 2 mm from the wound edge, perpendicular to the surface. If done properly, the suture will make a flask-shaped loop; the loop beneath the skin surface is farther apart than the entry and exit points on the surface. A needle exit in the middle of the wound is not necessary for small excisional wounds and for most punch wounds but depends upon the size of the needle and the ease that the wound edges can be approximated and everted.

To tie the suture, hold the needle holder parallel to the long axis of the wound with the free end and needle end of the suture on either side of the holder. Wrap the needle end of the suture twice around the holder, then grasp the free end of the suture with the holder and pull through, tightening the knot. At this point the needle end and free end of the suture should have switched sides relative to the beginning. The process is repeated as needed, reversing the position of the free end and needle end of the suture with each knot. "Approximate, don't strangulate" acknowledges the importance of proper tension on the suture. Excessive tension can be recognized by blanching of the wound edges and may indicate the need for subcutaneous sutures or simply less tension on each suture.

Placement of sutures for elliptical excisions can be facilitated by following the "rule of halves" [14]. The wound is divided in half by the initial suture placement, and each half is itself halved by the subsequent placement of sutures (figure 4). Similar halving continues until all wound edges are approximated. Starting the initial suture at an apex rather than the middle runs the risk of "dog ears" at the opposite apex owing to the creation of uneven wound edges.

The skin tension can be reduced in large wounds by placing a temporary initial suture at the midpoint of the wound, but farther from the edge than usual. At a later time, this suture can be removed as the wound is approximated with the permanent sutures.

Diamond and hexagonal excisions are easily closed by placing the initial sutures at the two opposing points of the diamond or four opposing points of the hexagon, then adding other sutures as necessary to completely approximate the wound. The straight lines of the diamond and hexagon provide better approximation of edges for the beginner than do the curved surfaces of the ellipse [4].

Wound dressing — Wounds heal faster when moist and under an occlusive or semiocclusive dressing [30]. Choices for topical occlusive ointments include plain petrolatum and antibiotic ointments (eg, bacitracin, mupirocin). Neomycin containing agents should be avoided due to the relatively high incidence of contact allergy. Contact dermatitis can also occur with bacitracin, although this occurs less frequently than with neomycin [31].

In a randomized trial, similar rates of infection were found in patients who used white petrolatum for postoperative wound care following dermatologic procedures compared with those who applied bacitracin [32]. Thus, to avoid the potential complication of contact dermatitis, we suggest the use of petrolatum for dressing clean wounds from skin biopsies and excisions.

All biopsy wounds should be dressed with a thin film of the occlusive ointment to prevent crust formation, then covered with an adhesive bandage or other nonadherent covering and topped with a gauze dressing and tape [14,30]. The dressing should be removed in 12 to 24 hours and cleaned with soap and water twice daily. After cleaning, the wound should be covered with the occlusive ointment. Wounds healing by secondary intention need to be redressed after each cleaning until healed over or for at least five days; covering the wound site is optional for sutured wounds. Showering is permitted after 24 hours for sutured wounds, but bathing and use of hot tubs are prohibited until the sutures are removed [33].

Suture removal — There is a balance between the tendency for wound dehiscence or stretching if the sutures are removed too early and the production of suture marks if they remain too long [10,29]. Sutures on the face generally can be removed in three to five days, followed by the application of semipermeable adhesive strips to reduce wound tension [14,29,30]. Sutures on the chest, abdomen, arms, and scalp can be removed in 7 to 10 days, and those on the back and legs in 12 to 20 days [14,29,30].

Clinicians should remove sutures from their patients to see the results of their suturing technique on wound healing. Crust should be washed away with wet gauze, then the suture gently lifted near the knot and one side cut close to the skin surface. The suture is removed by pulling across the wound surface; pulling away from the wound puts tension on the wound and may cause dehiscence [14].

BIOPSY OF PIGMENTED LESIONS — The possibility of malignant melanoma must always be considered when removing pigmented lesions. In the case of melanoma, adequate tissue sampling is important for accurate pathologic diagnosis, which includes assessment of the symmetry and architecture of the lesion, tumor size and depth, inflammation, and number of mitotic cells. As such, the preferred biopsy technique for pigmented lesions and lesions suspicious for or suggestive of melanoma is the excisional biopsy. Lesions suspected of being melanoma should include a 1 to 2 mm clinical margin. (See 'Excision' above and "Melanoma: Clinical features and diagnosis", section on 'Biopsy'.)

Small lesions (less than 4 mm in diameter) can be biopsied using the punch technique, provided that the entire lesion is removed with the punch. Elevated, nodular lesions should be biopsied by elliptical excision whenever possible. Deep shave or saucerization biopsies that extend well into the deep reticular dermis may be performed when excisions are not possible or practical [34]. This technique is appropriate for flat and large lesions and should be performed by clinicians with appropriate training and expertise; referral to a dermatologist or surgeon is preferred [35-37]. Ideally, the initial specimen should be removed to the level of subcutaneous fat to allow for proper staging if it is a melanoma.

Partial punch biopsies of lesions suspicious for melanoma are not generally recommended. Partial punch biopsies have a higher potential for misdiagnosis than other techniques and are less likely to provide accurate information for histologic staging of melanoma, which is important for management and prognosis [23,38]. Due to the possibility of sampling errors, close follow-up is warranted for lesions that are determined to be benign after a partial biopsy. Thus, lesions that appear too large for ease of biopsy by a primary care clinician should be referred to a dermatologist or surgeon. It is preferable to have the entire lesion removed at the time of biopsy, for both diagnostic and therapeutic purposes. Pigmented lesions should never be destroyed by cryosurgery or cautery, and all biopsy specimens should be submitted for histopathologic examination.

COMPLICATIONS — The major complications of skin biopsy include scarring, bleeding, infection, wound dehiscence, and allergic (primarily contact dermatitis) reactions:

Scarring is to be expected with any biopsy that extends into the reticular dermis. Clinicians should try to minimize scar appearance by careful selection of type, orientation, and location of biopsy when possible. Minimizing infection and chronic inflammation postbiopsy reduces the potential for hypertrophic scar formation and keloids, but unfavorable scars can result regardless, particularly on body sites and in patients prone to keloid formation [39]. Biopsies in areas of repeated skin movement (eg, joints) may result in spread scars.

Most bleeding can be controlled with simple pressure on the wound [4]. If this is not successful after five minutes, a single suture may be sufficient. If bleeding remains uncontrolled, remove the suture, find and tie off the bleeding vessel, then resuture.

Bleeding and hematoma formation can be minimized by using a pressure dressing directly over the wound [30]. Tape a folded 4 x 4 gauze pad tightly over the wound or secure it with an elastic bandage or self-adhering wrap. An ice pack applied for three to five minutes several times during the first 24 hours will also help decrease bleeding, hematoma formation, pain, and edema [30]. (See "Skin surgery: Prevention and treatment of complications", section on 'Intraoperative bleeding' and "Skin surgery: Prevention and treatment of complications", section on 'Hematoma'.)

Infection, though relatively uncommon, is usually the result of Staphylococcus, Streptococcus, or Candida [40]. If the wound is frankly purulent or has an associated cellulitis, culture the discharge and begin oral antibiotics. Infected wounds in the hands, feet, and intertriginous areas are often infected with Candida and can respond to topical antifungal ointments [40]. (See "Skin surgery: Prevention and treatment of complications", section on 'Surgical site infection'.)

Dehiscence (separation of wound edges) is infrequent but can occur when a wound becomes infected or with significant skin movement, such as in large excisional biopsies over a joint.

Patients may have allergic reactions to topical antibiotics [41]; the wound will be red, itchy, and may have vesicles. If this occurs, stop the antibiotic and apply a topical corticosteroid ointment. Most tape reactions are irritant, rather than allergic, and improve simply by not taping or sometimes by changing the direction of the tape on the skin [42]. (See "Skin surgery: Prevention and treatment of complications", section on 'Contact dermatitis'.)

DOCUMENTATION — All procedures must be documented in the medical record. Minimal content includes the location and nature of the lesion, indications for the procedure, what was done and how it was performed, specimen disposition, and instructions to and follow-up plans for the patient. Photographs of the lesion/biopsy site are frequently taken prior to the procedure for documentation purposes and may be required for insurance reimbursement. A photograph that orients the site with physical landmarks is helpful for subsequent location identification. This is particularly important when multiple biopsies are done in a region. The following are examples of patient instructions and procedure notes.

Sample patient instructions for wound care

Open wounds — The biopsy done today will heal from the bottom up and sides inward. Remove the adhesive bandage in 12 to 24 hours and clean it twice per day with soap and water. Apply a thin coat of petrolatum, unless otherwise instructed, then cover with an adhesive bandage. This type of wound heals faster when covered. If you have a lot of itching, redness, drainage of pus, swelling, or pain, call the office. Acetaminophen or ice packs may be used for pain control.

Sutured wounds — The biopsy done today has stitches that will need to be removed in _ days. Beginning tomorrow, remove the dressing, wash twice daily with soap and water, and then apply a thin film of petrolatum. Adhesive bandages are optional. Call the office if you experience significant redness, pain, itching, swelling, or drainage of pus. If you are unable to keep your appointment for suture removal, call the office. Acetaminophen or ice packs can be used for pain control.

Sample procedure notes

Shave biopsy — The possible diagnosis of basal cell carcinoma and need for biopsy confirmation was discussed with the patient, and consent for a shave biopsy of the left ear was obtained. Photograph was obtained. The skin was prepped with alcohol; local anesthesia was obtained with 1% lidocaine with epinephrine and NaHCO3. A shave biopsy into the dermis was performed with a razor, and hemostasis was achieved with AlCl3. The biopsy specimens were submitted to pathology in formalin. Petrolatum and an adhesive bandage dressing were applied. Wound instructions were given. The patient will return in two weeks for a wound check and review of pathology results.

Punch biopsy — A possible diagnosis of lupus was discussed with the patient and the need for two biopsies reviewed. Consent for the procedure was obtained. Photographs were obtained. The skin of the right upper, inner, and outer arm was prepped with chlorhexidine and alcohol, and local anesthesia was obtained with 1% lidocaine with epinephrine and NaHCO3. Two 4 mm punches extending into subcutaneous fat were obtained from the right deltoid area and the right medial arm above the antecubital area. Each site was closed with one 4-O nylon suture. The specimen from the deltoid area was placed in formalin and from the medial arm into Michel's solution and submitted to pathology. Adhesive bandage dressings were applied. Wound care instructions were given. The patient will return in 10 days for suture removal and review of pathology results.

Elliptical excision — Description: atypical nevus 8 x 4 mm left upper back. The possible diagnosis, procedure, need for biopsy, potential complications, side effects, and scarring were discussed with the patient and consent for the procedure was obtained. Photograph was obtained. The patient was placed in the prone position, local anesthesia was achieved using 1% lidocaine with epinephrine 1:100,000 and NaHCO3, and the skin was prepped with povidone-iodine and alcohol and draped in the usual sterile fashion. The lesion and a 2 mm clear-appearing margin was excised in an ellipse to the depth of the subcutaneous tissue. Wound edges were undermined bluntly, three 4-O Vicryl inverted mattress sutures were placed in the dermis. The wound was closed with five 4-O nylon sutures. A pressure dressing was applied. Wound care instructions were given. The specimen was sent to pathology in formalin. Final wound length 2.5 cm. The patient tolerated the procedure well. She will return in 14 days for suture removal and review of pathology results.

SUMMARY AND RECOMMENDATIONS

The skin biopsy is a simple procedure that can assist with the diagnosis of cutaneous disorders. Skin biopsies may be performed with shave, punch, or excisional techniques. The type of skin lesion and the location of the biopsy are important factors to consider when choosing which procedure to perform. (See 'Site selection' above and 'Choice of procedure' above.)

The most common anesthetic used for skin biopsies is lidocaine. Lidocaine and epinephrine may be used to induce vasoconstriction, which decreases bleeding and prolongs anesthesia. Several techniques are useful for decreasing the pain associated with injection. (See 'Anesthesia' above.)

Shave biopsies are typically used for lesions for which sampling of the full thickness of the dermis is not necessary. Shave biopsies are performed with a number 15 scalpel blade or a razor blade. Aluminum chloride or another topical hemostatic agent is used to control bleeding. (See 'Choice of procedure' above and 'Shave biopsy' above.)

Punch biopsies involve the removal of a core-shape piece of tissue and allow sampling of the deep dermis. Punch biopsy wounds can be closed with suture or left to heal by secondary intention. (See 'Choice of procedure' above and 'Punch biopsy' above.)

Excisions are more time consuming than punch or shave biopsies, but are useful for biopsies of larger or deeper lesions. Careful technique is necessary to achieve a good cosmetic result and to reduce the risk of complications. (See 'Choice of procedure' above and 'Excision' above.)

Excisional biopsy is the preferred procedure for biopsy of pigmented lesions that are suspicious for melanoma. Only clinicians who are experienced with the deep shave or saucerization biopsy technique should perform this procedure on pigmented lesions. (See 'Biopsy of pigmented lesions' above.)

Clinical information is useful for pathologists as they interpret the findings in skin biopsies. A clinical description of the lesion and brief history should be submitted with a biopsy specimen. (See 'Processing the biopsy sample' above.)

Wound care for a skin biopsy site should involve the application of an occlusive ointment. Potential complications of skin biopsy include bleeding and infection. Allergic reactions to topical antibiotics may also occur. (See 'Wound dressing' above and 'Complications' above.)

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Topic 5577 Version 17.0

References