Residency · Residency · Family Medicine

Skin Procedures: Biopsy, Cryotherapy, and Excision

Introduction

Dermatologic procedures are among the most frequently performed office procedures in family medicine. Competence in skin biopsy, cryotherapy, and excision enables family physicians to diagnose suspicious lesions, treat benign growths, and manage common skin conditions without specialty referral. Proper technique, specimen handling, and follow-up are essential for optimal outcomes.

Skin Biopsy

Indications

Skin biopsy is indicated for any lesion suspicious for malignancy, including changing moles, non-healing ulcers, and new pigmented lesions. Rashes of uncertain etiology that are unresponsive to empiric treatment warrant biopsy, as does the need for confirmation of a clinical diagnosis such as psoriasis, lichen planus, or vasculitis. Monitoring of chronic conditions including lupus and dermatomyositis may also require periodic biopsy.

Biopsy Techniques

Shave Biopsy

Shave biopsy is best suited for raised, superficial lesions such as seborrheic keratoses, skin tags, superficial basal cell carcinoma, and suspected squamous cell carcinoma in situ. The technique involves injecting local anesthetic (lidocaine 1% with epinephrine) beneath the lesion to create a wheal, then using a flexible razor blade or DermaBlade held tangentially to shave the lesion at the level of the surrounding skin or slightly deeper. Shave biopsy should be avoided for melanocytic lesions suspicious for melanoma because transection may compromise Breslow depth measurement. Hemostasis is achieved with aluminum chloride 20 to 35% (Drysol) or electrocautery.

Punch Biopsy

Punch biopsy is best suited for inflammatory dermatoses, deeper lesions, small well-defined lesions, and melanocytic nevi. A disposable punch tool, typically 3 to 4 mm in diameter (range 2 to 6 mm), is applied perpendicular to the skin with gentle downward pressure and rotation. The specimen is removed with forceps and iris scissors, with gentle tissue handling to avoid crush artifact. Punches 3 mm or smaller may heal by secondary intention, while those 4 mm and larger are typically closed with one to two simple interrupted sutures. The punch should be oriented along relaxed skin tension lines for optimal cosmetic closure.

Excisional Biopsy

Excisional biopsy is best suited for lesions suspicious for melanoma where full-thickness removal with narrow margins is needed for accurate staging. It includes the entire lesion with a 1 to 3 mm margin of normal-appearing skin and requires the elliptical excision technique described below.

Specimen Handling

Specimens are placed in 10% formalin for routine histopathology. Michel transport medium is used for direct immunofluorescence when autoimmune blistering disease is suspected. The container should be labeled with the patient name, date, anatomic site, and clinical description, and relevant clinical information should be included on the pathology requisition.

Cryotherapy

Mechanism

Liquid nitrogen at -196 degrees Celsius causes rapid freezing of tissue, leading to intracellular ice crystal formation, cell membrane disruption, and tissue necrosis. It is applied via cotton-tipped applicator, cryospray unit, or cryoprobe.

Indications

The most common indication is actinic keratoses, which are precancerous lesions. Verrucae (warts), including common, plantar, and flat variants, respond to cryotherapy. Other indications include seborrheic keratoses treated for cosmetic or symptomatic reasons, molluscum contagiosum, skin tags (acrochordons), and select small superficial basal cell carcinomas in non-facial, low-risk locations.

Contraindications

Lesions of uncertain diagnosis should be biopsied before treatment. Cold-sensitive conditions such as cryoglobulinemia, cold urticaria, and Raynaud phenomenon are contraindications. Lesions over areas with poor circulation, such as digits in patients with peripheral vascular disease, should not be treated with cryotherapy. Darkly pigmented skin carries a higher risk of permanent hypopigmentation, and patients should be counseled accordingly.

Technique

Anesthesia is typically not required for small lesions, though lidocaine may be considered for larger or sensitive areas. The freeze-thaw-freeze technique using two cycles is more effective than a single freeze for warts and actinic keratoses. The goal is to achieve an ice ball extending 1 to 2 mm beyond the lesion border. Typical freeze times are 5 to 10 seconds per cycle for actinic keratoses and 10 to 20 seconds per cycle for warts. The cryospray nozzle should be held 1 to 2 cm from the skin surface.

Post-Procedure Care

Patients should expect erythema, edema, and blister formation within hours. The blister may be hemorrhagic, which is normal and does not require drainage unless symptomatic. Petroleum jelly and a bandage should be applied, and the area kept clean and dry. Healing typically occurs over one to three weeks. Hypopigmentation is the most common long-term side effect, and darkly pigmented patients should be counseled about this risk. Warts often require repeat treatments at two- to three-week intervals.

Excision

Indications

Excision is indicated for suspected melanoma or lesions requiring a full-thickness specimen with margins, lipomas, epidermal inclusion cysts, and other subcutaneous masses, benign lesions causing symptoms such as pain, irritation, or cosmetic concern, and non-melanoma skin cancer when Mohs surgery is not indicated.

Elliptical Excision Technique

Planning

The long axis of the ellipse should be oriented along relaxed skin tension lines (Langer lines) for optimal scar cosmesis. A 3:1 length-to-width ratio prevents dog ears (standing cone deformities). Surgical margins should be marked before anesthesia because tissue distortion occurs after injection. Appropriate margins are 1 to 2 mm for benign lesions, 3 to 4 mm for basal cell carcinoma, 4 to 6 mm for squamous cell carcinoma, and 5 mm for melanoma in situ (with definitive excision typically performed by dermatology or surgery).

Procedure

Lidocaine 1% with epinephrine is injected, with traditional teaching to avoid epinephrine on digits, the tip of the nose, ears, and penis, though evidence supports safe use on digits. A 7- to 10-minute wait allows full anesthetic and vasoconstrictive effect. The incision is made with a number 15 scalpel blade held perpendicular to the skin along the marked ellipse. Undermining in the subcutaneous fat plane using iris scissors or scalpel allows tension-free closure. Hemostasis is achieved with electrocautery, pressure, or suture ligation. Layered closure involves deep dermal sutures (4-0 or 5-0 absorbable polyglactin/Vicryl) to reduce tension, followed by skin sutures (simple interrupted or running) or adhesive strips.

Suture Selection

Post-Procedure Wound Care

The wound should be kept clean and dry for 24 hours, then gently washed with soap and water daily. Petroleum jelly and a non-stick bandage should be applied until suture removal. Patients should avoid heavy lifting or strenuous activity for two weeks on trunk and extremities. Signs of infection requiring evaluation include increasing pain, expanding erythema, purulent drainage, and fever.

Complications

Potential complications include bleeding and hematoma, wound infection (1 to 5%), hypertrophic scar or keloid formation, nerve damage (particularly on the face), and dog ear deformity requiring revision.

Key Clinical Pearls

Never shave biopsy a lesion suspicious for melanoma; an excisional biopsy with narrow margins is required to accurately determine Breslow depth. When in doubt about a lesion, biopsy first and treat second, as clinical diagnosis alone misses a significant percentage of skin cancers. Cryotherapy of actinic keratoses is highly effective but requires adequate freeze time and often repeat treatment; incomplete treatment leads to recurrence. Excision margins should be marked before injecting local anesthetic to avoid distortion of landmarks. All excised tissue should be sent for histopathologic examination, even for clinically benign-appearing lesions.

References

1. Zuber TJ. Punch biopsy of the skin. Am Fam Physician. 2002;65(6):1155-1158.
2. Andrews MD. Cryosurgery for common skin conditions. Am Fam Physician. 2004;69(10):2365-2372.
3. Otley CC, Fewkes JL. Complications of cutaneous laser surgery: a review. Dermatol Surg. 2002;28(9):751-756.
4. Neville JA, Welch E, Leffell DJ. Management of nonmelanoma skin cancer in 2007. Nat Clin Pract Oncol. 2007;4(8):462-469.

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