Skin Biopsy Techniques - An Overview

What Is a Skin Biopsy?

Skin biopsy is a safe and easy diagnostic procedure that forms the basis for the treatment of benign and malignant lesions in the skin; it also acts as documentary evidence for the diagnosis in the era of evidence-based medicine.

There are various techniques to perform a skin biopsy, and all of them are done in a dermatological setting. Choosing the appropriate technique will give the consulting pathologist the highest chance of diagnostic yield, at the same time causing little to no disfigurement to the patient.

Who Is Advised to Get a Skin Biopsy?

The clinician will request a skin biopsy if he suspects any of the below-mentioned conditions-

• Bullous pemphigoid and other blistering skin disorders.

• Actinic keratosis presents as rough and scaly patches on the skin of older adults.

• Skin tags.

• Warts.

• Skin cancers include squamous cell carcinoma, melanoma, basal cell carcinoma, etc.

• Inflammatory skin disorders.

• Occasional skin infections.

• Suspicious moles.

• Systemic diseases that have skin or soft tissue manifestations.

However, a skin biopsy is not preferred in patients who are allergic to local anesthesia, have a tattoo, or have an infection that will lead to challenges.

What Are the Different Techniques of Skin Biopsy?

Choosing the right technique depends on choosing the right lesion; a right lesion is one that is well-formed and non-modified either by scratching or any topical application. A few exceptions to these rules are-

• Henoc Schonlein Purpura- An early lesion is preferred for biopsy in the conditions because it better demonstrates leukocytoclasis (accumulation of neutrophils) and IgA deposition in the vessel wall.

• Dermatitis Herpetiformis- A premature dermal papilla formed in dermatitis herpetiformis will demonstrate a better collection of neutrophils at its tip.

• Subepidermal Blisters- Well-defined older blisters are avoided in the biopsy for suspected subepidermal blisters because the old ones undergo reepithelialization, which will make them look like intraepidermal blisters, thereby altering the diagnosis.

After choosing the ideal lesion, the next crucial step is anesthetizing the location; Lidocaine with Adrenaline is the popular choice that can be given as infiltration or a peripheral nerve block. In conditions where in-depth numbness is required for a longer duration, a eutectic mixture of local anesthetics (EMLA) is used. It achieves a depth of 5 mm for two hours, which is sufficient time for a biopsy on the chest, abdomen, face, and genitals.

After anesthesia comes the biopsy technique. This depends on the location and type of the lesion and the proficiency of the technician. There are six different types of skin biopsy techniques-

1. Punch Biopsy- It is the most preferred method for diagnostic and therapeutic purposes of small pyogenic granuloma, verruca, tattoo, etc. After anesthetizing the area, the skin is held taut in a perpendicular direction to the surrounding skin.

   • This converts the round lesion into an oval one, thereby reducing the chances of dog ear formation. A special tool called the punch is pushed into the skin by rotatory movements; this will give entry into the subcutaneous plane. Once a ‘give away’ feel is perceived, indicating the collection of the specimen (containing epidermis, dermis, and superficial fat), the punch is removed, and the resulting wound is sutured off.

   • If this technique is being done on areas with thin skin and overlying bone, care should be taken not to injure the periosteum, which will cause severe pain and discomfort.

   • Ease of performance and uniform specimen are the advantages of this technique, whereas inadequate and insufficient specimen are the disadvantages.

2. Shave Biopsy- It is used for superficial lesions like seborrheic keratosis, where the portion of the lesion present above the level of the surrounding skin is shaved off using a blade. It is avoided for lesions that require deeper tissue.

3. Saucerization Biopsy- This technique is preferred for vesiculobullous lesions and for epidermal neoplasms like seborrheic keratosis. The procedure is done with a shaving blade held in between the thumb and the index finger so that the blade is bent in the form of an arc.

   • The blade is introduced deep enough to scope through the dermis; once the lesion is cropped completely in this manner, the wound is dressed up.

4. Wedge Biopsy- This technique is performed for suspected lesions of subcutaneous mycosis, squamous cell carcinoma, tuberculosis verrucosa cutis, etc., where large lesions in terms of length, breadth, and depth are required for the biopsy.

   • After anesthesia, a stab incision in the form of a “V” or a triangle is made with a scalpel, followed by extracting a wedge-shaped specimen. The wound is then dressed and left to heal.

5. Incisional Biopsy- It is done when inflammatory dermatosis or porokeratosis is suspected. An incision is made and extended into the surrounding normal tissue; occasionally, it can be expanded from the center of the lesion to the raised margin into the surrounding tissue, thereby making all three zones visible.

6. Excisional Biopsy- As the name suggests, the entire lesion is excised and used as a specimen for diagnosis, most commonly done for neoplasms. The wound is closed with sutures post excision.

The above-mentioned are standard techniques for skin biopsy, but sometimes, there are chances of modulating the techniques to suit the needs of an atypical lesion; some of them are-

• In cases of suspected urticaria pigmentosa, local infiltration of anesthesia will degranulate the mast cells of the lesion. This should be avoided because the mast cells are important from a diagnostic aspect; the damage can be prevented by replacing the local infiltration with a filed block.

• In a scalp biopsy, the punch should be done in the direction parallel to the emerging hairs of the scalp, and the blood vessels around the lesion should be compressed by pressing the needle holder around the lesion.

• For vesiculobullous lesions that require biopsy for immunofluorescence, the perilesional normal skin is taken instead of the involved skin.

• For lupus erythematosus, three biopsies, including lesional skin, non-lesional sun-exposed skin, and non-lesional sun-protected skin, should be taken as samples.

• For vascular lesions in the shaft or glans penis, it is advised to use an anesthetic without adrenaline to prevent bleeding.

What Are the Complications of Skin Biopsy?

It is a safe and well-tolerated diagnostic procedure that is occasionally accompanied by a few complications; they are-

• Hypersensitivity to local anesthetics.

• The pain of local anesthesia.

• Bleeding.

• Scarring.

• Infection.

Performing a patch test prior to the procedure will prevent the sensitivity to the anesthetic, and the rest of the complications can be avoided with primary suturing and antibiotic dressing.

Conclusion:

Skin biopsy has a great diagnostic value in spite of being a simple procedure. Knowing the practical aspects, along with awareness of the complications that might arise from the skin biopsy techniques, will help the clinician in terms of arriving at a diagnosis and providing necessary information regarding the disease.