Skin Biopsy 

Updated: Mar 04, 2018
Author: Chad L Prather, MD; Chief Editor: Dirk M Elston, MD 

Overview

Background

Skin biopsy is performed in order to obtain tissue for further examination in the laboratory, typically through microscopy or tissue culture. Because of the relatively low risk of skin biopsy as compared with biopsy of other organs, and the ability to obtain a sample under simple local anesthesia, a skin biopsy can be safely and routinely performed in an outpatient or ambulatory setting, as well as an inpatient setting. The usual intent of skin biopsy is to further characterize the nature of a skin growth or eruption and assist in diagnosis by allowing histopathologic evaluation of a tissue sample.

After local anesthetic is administered, the tissue is removed and placed in a specimen container with an appropriate fixative, usually 10% formalin for permanent section diagnosis or Michel’s solution for immunofluorescence. The specimen is then sent to a pathology laboratory, where, after tissue fixation, slide preparation, and staining, a pathologist, dermatologist, or dermatopathologist can examine the specimen under a microscope. Alternatively, the tissue is placed in normal saline rather than a fixative for viral or bacterial laboratory cultures.

Indications

A skin biopsy is indicated to evaluate cutaneous growths when malignancy is a concern or to confirm the type of a known malignant growth (eg, basal cell carcinoma, squamous cell carcinoma, melanoma) prior to a more invasive surgical procedure.

Skin biopsies are also indicated for cutaneous eruptions to help clarify the diagnosis when multiple etiologies are being considered.[1] The best biopsy to assess an eruption, as opposed to a tumor or growth, is a punch biopsy owing to the ability to evaluate the epidermal, dermal, and subcutaneous tissue for histological examination. A punch biopsy is accomplished with a circular or elliptically shaped blade that is driven vertically into the skin in a direction perpendicular to the cutaneous plane, usually to the level of the subcutaneous tissue. The punch instrument can be used for diagnostic and therapeutic purposes. By definition, a biopsy is used to sample tissue in order to investigate a clinical lesion or eruption further, but not necessarily to attempt complete lesion removal. At times, however, a punch biopsy removes the entire skin lesion.

A shave biopsy, in which a blade is used to remove epidermis and partial or complete dermis with a horizontal and partially oblique direction, allows for evaluation of the epidermis with or without the superficial dermis but does not provide a great representation of the subcutaneous tissue compared with other biopsy methods.

The image below depicts skin anatomy.

Anatomy of the skin. Anatomy of the skin.

Contraindications

Skin biopsy is rarely contraindicated.

Precautions should be taken if a patient has a history of an allergy to local or topical anesthetics or has evidence of an active infection at the biopsy site. Prebiopsy evaluation should also include a history for any bleeding disorders, medications that might affect hemostasis through their anticoagulative effects, or prior history of bleeding problems after a surgery or procedure, which may indicate an intrinsic clotting factor deficiency. Such factors do not preclude skin biopsy, but may prolong or complicate hemostasis.[2]

Complications

Complications to skin biopsies include bleeding at the biopsy site, hematoma, or infection. Pressure dressings and ice can be used to help alleviate symptoms associated with bleeding or hematomas. In some cases, a suture is used to aid in hemostasis, particularly after a punch biopsy greater than 3-4 mm in width. Clean uncontaminated skin procedures are associated with low rates of surgical site infection (overall incidence of < 5%).[3] Some locations of the body are associated with higher infection rates, and guidelines have been proposed for these cases.[4] Although uncommonly necessary, antibiotics can be started in the event of a resulting infection.

Some patients might experience a hypersensitivity reaction, with evidence of erythema, pruritus, or vesicles. A vasovagal response is usually a self-limited hypotension with possible peripheral vasodilation that could result in lightheadedness, sweating, nausea, and/or fainting. At the first sign of an impending vasovagal episode, the patient should be placed in a supine position with the legs higher than the upper body or a Trendelenburg position. A moist cloth can be applied with continuous observation of the patient to prevent possible injury until he or she recovers.[5]

Outcomes

The area of biopsy heals with some degree of scarring, and this should be discussed with the patient beforehand. A shave biopsy heals over the course of several weeks with crusting, eschar, and some minimal temporary pain during the course of healing. It ultimately leaves a hypopigmented or hyperpigmented scar roughly the size of the shave biopsy; the scar may be depressed depending on the depth of the shave biopsy. A punch biopsy also typically heals with a smaller, round scar, usually slightly smaller than the size of the punch instrument used. Healing time for a punch biopsy may be shortened and the scar may be lessened by using sutures to close the full-thickness wound.

 

Periprocedural Care

Patient Education and Consent

Patients should be informed about the need for biopsy, why it is recommended (eg, to help establish diagnosis and formulate a treatment plan), and the anticipated risks and benefits prior to performing a skin biopsy. In this manner, they can help decide whether or not a biopsy is warranted and give their informed consent. Specifically, patients should be informed of the anticipated healing process following a particular type of biopsy and the degree of scarring that will likely result.

Equipment

Equipment used to perform a skin biopsy includes the following:

  • Alcohol wipe to clean the area for biopsy

  • Syringe with a 30-gauge needle and anesthetic

  • Gloves
  • Surgical forceps, preferably toothed to minimize crush artifact
  • Pathology container filled with 10% formalin solution or normal saline and laboratory requisition form

  • Gauze, 2 X 2-inch or 4 X 4-inch

Dressing materials include the following:

  • Petrolatum or antibiotic ointment

  • Bandage or nonstick bandage and tape

The following is used for a punch biopsy (see image below):

  • Disposable punch instrument ranging from 2-8 mm in size

  • Scissors

  • Needle holder for suturing

  • Desired size of suture

    Equipment used for a punch biopsy. Equipment used for a punch biopsy.

The following is used for a shave biopsy (see image below):

  • Surgical blade (No. 15) and scalpel handle or disposable razor blade

    Equipment used for a shave biopsy. Equipment used for a shave biopsy.

Supplies for hemostasis include the following:

  • Chemical cauterization: Solution of 20-50% aluminum chloride (Drysol) or ferric subsulfate (Monsel solution)

  • Electrical cauterization: Electrodessication, electrofulguration, or electrocoagulation may also be used

Patient Preparation

Skin preparation

Alcohol, chlorhexidine, and povidone-iodine solution are the most commonly topical products used to clean the skin in preparation for skin biopsy. These may be used in a simple manner to wipe the immediate area of biopsy.

Anesthesia

Most skin biopsies are performed using a local anesthetic agent injected into the dermal and subcutaneous layers of the skin, usually with a small (1- or 0.5-inch) 30-gauge needle. Local anesthetics are divided into two categories known as the esters and the amides, which differ in structure and method of metabolism. Although allergies to local anesthetics are rare, adverse reactions to the ester class are more prevalent. Therefore, the amide class, which includes lidocaine, is more commonly used.[6] Hemostasis can be improved with the addition of epinephrine in dilutions of 1:100,000, 1:200,000, or 1:500,000.[7] Pain during injection can be decreased by buffering the solution with sodium bicarbonate to achieve a less acidic pH,[5] by warming the anesthetic to body temperature,[8] by using a small needle, and by injecting the anesthetic solution very slowly.

Alternatives to locally injected anesthetics for purposes of skin biopsies include topically applied amide anesthetic creams, topically applied cold agents (eg, ice, ethyl chloride, small amounts of liquid nitrogen), or injection with saline with benzyl alcohol (preservative).[9]

Topically applied creams are the most common method used after injection. Eutectic mixture of local anesthetics (EMLA) cream is a mixture of lidocaine and prilocaine that is an alternative to injection. It must be occluded after application and requires a minimum application time of 60 minutes. Four or 5% lidocaine-only creams are also commercially available, do not require occlusion, and usually require at least 30 minutes of application for effect. Topical anesthesia may be adequate for superficial shave biopsies, but injection is usually faster and more thorough.

Unfortunately, topical creams do not achieve moderate to deep penetration necessary for deeper punch, incisional, or excisional biopsies. As such, they are not alone sufficient for such procedures, but may help ease the discomfort of locally injected anesthetics prior to deeper procedures or in children.[5]

Preprocedural Planning

The area where the biopsy will be performed may be marked with gentian violet, but this in not required prior to biopsy. High-quality photographs of the area with an adequate resolution to demonstrate clinical appearance and an appropriate field of view that allows the area of biopsy to be seen in the context of surrounding skin or anatomic markings should be obtained prior to biopsy. This assists with relocating the area in the future, after healing, should it need to be reidentified. For example, if the biopsy shows squamous cell carcinoma and further excisional surgery is needed, appropriate clinical photographs may help identify the correct site for surgery on a background of diffusely sun-damaged skin.

Monitoring & Follow-up

Patients may be sent home for self-care following a skin biopsy and should be advised to do simple local wound care, typically with a gentle wash and topical petrolatum ointment. If sutures are placed, these should be removed in 1-2 weeks as appropriate. Pathology or culture results should be communicated to the patient in a timely manner following biopsy so that further care for the diagnosis can be achieved.

 

Technique

Approach Considerations

Skin biopsies can be performed using various methods, including tangential shave, punch, incisional, or excisional techniques. A punch biopsy is performed with cylindrical instruments that can range from 2-8 mm. An advantage of a punch biopsy is the ability to evaluate into the subcutaneous fat. When choosing the appropriate instrument, how much tissue is necessary to obtain an adequate diagnosis while causing the least obvious cosmetic defect should be considered.[10]

Punch Biopsy

Once the area of the punch biopsy is selected, it is often helpful to outline the area prior to the procedure. Local anesthetics can blanch the skin, making it difficult to determine the intended biopsy location. The procedure can be performed using clean disposable examination gloves rather than sterile gloves. This enables the physician to perform the procedure and to administer the anesthetic in a sterile fashion without a completely sterile field.

After preparation of the site, the skin is stretched perpendicular to the lines of least skin tension so that the wound forms an oval.[10] While holding the stretched skin taunt, the punch instrument is introduced vertically using a smooth twisting motion. Once the instrument reaches its maximum depth or goes through the dermis and into the subcutaneous tissue, the punch can be removed. When removing the tissue specimen, caution should be taken to avoid crushing the biopsied tissue by using fine single-toothed forceps or the 30-guage needle used for anesthetic injection.

The wound may be closed and hemostasis achieved by gel foam or by suture. Gel foam is indicated as a hemostatic device for use with surgical procedures. The wound may also be closed with nonabsorbable suture to aid in hemostasis and to produce a better aesthetic result.[5]

The images below depict illustrations of a punch biopsy being performed.

Illustration of punch biopsy being performed. Illustration of punch biopsy being performed.
Illustration of punch biopsy being performed. Illustration of punch biopsy being performed.

Shave Approach

When tissue sampling is limited to the epidermis and superficial dermis, a shave biopsy may be considered. The lesion can be elevated by intradermally injecting anesthesia into the surrounding area to produce a wheal. The skin is held taut by applying pressure to the skin with a slight lateral pull.

A No. 15 surgical blade on a scalpel handle or disposable, flexible single razor blade can be used to horizontally transect the lesion at the base using a steady cutting motion. The depth of the sample can be controlled by adjusting the angle of the blade.[5] Once removed, the tissue can be marked with inks or a suture for orientation or simply placed in the bottle containing a formalin fixative and transported to the laboratory. A styptic agent such as aluminum chloride or ferric sub sulfate solution and a bandage is then applied to control bleeding.

The images below depict illustrations of a shave biopsy being performed.

Illustration of a shave biopsy being performed. Illustration of a shave biopsy being performed.
Illustration of shave biopsy being performed. Illustration of shave biopsy being performed.