What is the procedure for performing a punch biopsy?

How to Perform a Punch Biopsy

A punch biopsy should be performed as a full-thickness skin biopsy that includes the whole lesion with a 2-5 mm clinical margin of normal skin laterally and with a cuff of subdermal fat to allow for accurate diagnosis and staging. 1

Equipment and Preparation

• Circular punch tool (typically 3-4 mm diameter)
• Local anesthetic (lidocaine, with or without epinephrine)
• Sterile gloves
• Antiseptic solution
• Gauze
• Forceps
• Scissors
• Suture material
• Dressing supplies

Step-by-Step Procedure

1. Site Selection

• Choose an area that is representative of the lesion
• For suspected melanoma, select the thickest portion of the lesion 1
• For large lesions where complete excision isn't possible, biopsy the most suspicious area 1
• Avoid areas of necrosis, ulceration, or previous trauma when possible

2. Preparation

• Clean the area with antiseptic solution
• Drape the area if needed
• Administer local anesthesia (1-2% lidocaine with or without epinephrine)
  • Avoid epinephrine for lesions on the face, genitalia, or digits 1

3. Biopsy Technique

1. Hold the punch tool perpendicular to the skin surface
2. Stretch the skin perpendicular to the lines of least skin tension to create an elliptical wound for easier closure 2
3. Apply downward pressure while rotating the punch tool in a clockwise-counterclockwise motion
4. Continue until you feel decreased resistance, indicating penetration into subcutaneous fat
5. The punch should penetrate through the epidermis, dermis, and into subcutaneous fat 2

4. Specimen Retrieval

• Gently lift the core with forceps or a needle, grasping the subcutaneous portion (not the epidermis)
• Avoid crushing the specimen to prevent artifact 3
• If forceps are unavailable, a towel clip can be used as an alternative 4
• Another technique involves rotating the punch 90 degrees then lateral extraction with upward traction 3
• Cut the base of the specimen at the level of subcutaneous fat with scissors

5. Specimen Handling

• Place the specimen directly into appropriate fixative (usually formalin)
• Handle minimally to avoid crush artifact
• For suspected leishmaniasis, avoid leaving residual iodine or alcohol on the specimen as it may interfere with culture yield 1

6. Wound Closure

• For 3-4 mm punches, close with a single simple interrupted suture
• For larger punches, two or more sutures may be needed
• Alternatively, small punch sites may heal by secondary intention

7. Post-Procedure Care

• Apply pressure if needed to control bleeding
• Apply appropriate dressing
• Provide wound care instructions to the patient

Special Considerations

For Different Lesion Types:

• Melanoma: Excisional biopsy with 1-3 mm margins is preferred. Punch biopsy is acceptable for facial or acral lesions, very large lesions, or when complete excision isn't feasible 1
• Basal Cell Carcinoma: Punch biopsy should be adequate to provide clinical information and pathology elements to permit accurate diagnosis 1
• Lentigo Maligna: Initial incisional biopsy is appropriate for changing flat pigmented lesions on the face 1
• Leishmaniasis: Obtain samples from a cleansed lesion from which cellular debris and eschar/exudates have been removed 1

Common Pitfalls to Avoid:

1. Inadequate depth: Ensure the punch extends into subcutaneous fat
2. Crush artifact: Handle specimens minimally and with care 3
3. Inappropriate site selection: Choose representative or thickest portion of lesion
4. Inadequate specimen size: Use 3-4 mm punch for diagnostic purposes 5
5. Shave biopsy for melanoma: This may compromise accurate Breslow thickness assessment 1

Documentation

Include in the pathology request:

• Patient demographics
• Anatomic location of lesion
• Clinical appearance and size
• Relevant clinical history
• Differential diagnosis
• Type of procedure performed

By following these steps, you can perform an effective punch biopsy that provides adequate tissue for histopathological diagnosis while minimizing scarring and patient discomfort.