When should a shave biopsy versus an excisional biopsy (excisional biopsy) be performed for skin lesions?

Shave vs Excisional Biopsy: When to Use Each Technique

For suspected melanoma, perform a narrow excisional biopsy with 1-3 mm margins as the preferred technique; superficial shave biopsies are generally discouraged except for macular lesions suggestive of melanoma in situ, lentigo maligna type, where a deep/broad shave biopsy extending into the deep papillary or superficial reticular dermis is acceptable. 1

Primary Decision Algorithm for Suspected Melanoma

Excisional Biopsy is Preferred When:

• Any raised or nodular lesion concerning for melanoma - Complete excision with 1-3 mm margins extending to sufficient depth to prevent transection at the base is the gold standard 1
• The excision can be accomplished by:
  • Fusiform/elliptical excision 1
  • Punch excision around the clinical lesion 1
  • Deep shave/saucerization to depth below the anticipated plane of the lesion 1

Critical rationale: Superficial shave biopsies may underestimate Breslow thickness and clinical stage, potentially leading to incorrect staging and treatment planning 1

Shave Biopsy (Deep/Broad) is Acceptable When:

• Macular lesion suggestive of melanoma in situ, lentigo maligna type - A broad shave biopsy extending into the deep papillary or superficial reticular dermis provides more thorough histologic assessment of potential focal microinvasion than multiple punch biopsies 1
• The shave must be deep enough (saucerization technique) to adequately sample the dermis 1

Partial/Incisional Biopsy is Acceptable in Select Circumstances:

• Facial location where complete excision would be cosmetically or functionally problematic 1
• Acral location (palms, soles, nail apparatus) 1
• Very large lesions where complete excision is not initially feasible 1
• Low clinical suspicion or diagnostic uncertainty 1

Important caveat: Partial biopsy may inaccurately stage melanoma at the outset and negatively affect treatment planning 1

Special Anatomic Considerations

Nail Lesions:

• Suspicious nail lesions (melanonychia striata, diffuse pigmentation, amelanotic changes) require nail matrix sampling 1
• The nail plate should be sufficiently removed to expose the underlying lesion 1
• Excisional or incisional biopsy performed depending on lesion size 1
• These biopsies should be performed by practitioners skilled in nail apparatus biopsy 1

Subungual Lesions:

• Remove nail plate adequately to allow proper sampling of the nail matrix 1
• Biopsy clinically obvious tumor if present 1

Critical Pitfalls to Avoid

Never Perform Superficial Shave Biopsy for Suspected Invasive Melanoma:

• Diagnostic shave biopsies should not be performed as they lead to incorrect diagnosis due to sampling error and make accurate pathological staging impossible 1
• This is the most common error that compromises patient outcomes 1

Avoid Partial Removal of Benign-Appearing Nevi:

• Partial removal of a melanocytic nevus may result in pseudomelanoma (clinical and pathological picture resembling melanoma), causing needless anxiety 1, 2
• For atypical nevi, shave biopsy is acceptable as these are frequently diagnosed using this technique 2

Re-excision Considerations:

• Narrow-margin excisional biopsy may be performed if initial partial biopsy is inadequate for diagnosis or microstaging 1
• However, it should not generally be performed if the initial specimen meets criteria for consideration of sentinel lymph node biopsy 1

Technical Execution Details

For Excisional Biopsy:

• Include 1-3 mm peripheral margin around the concerning lesion 1
• Extend to sufficient depth to ensure the lesion is not histologically transected at the deep margin 1
• Include a cuff of fat 1
• Orient the excision axis to facilitate possible subsequent wide local excision (generally along the long axis on limbs) 1

For Deep Shave/Saucerization:

• Must extend into deep papillary or superficial reticular dermis 1
• Use topical hemostatic agents (aluminum chloride or ferric subsulfate) preferred over electrocautery 1
• Absorbable gelatin coagulants can be added 1

Documentation Requirements

• Pre-biopsy photographs are essential - Include regional photograph with anatomic landmarks to aid clinical/pathologic correlation and prevent wrong-site surgery 1
• Provide pertinent clinical information to pathologist including level of suspicion for melanoma, clinical description, and lesion history 1

Evidence Quality Note

While one retrospective study suggested shave biopsy accuracy of 97% for melanomas <2mm 3, the American Academy of Dermatology guidelines explicitly discourage superficial shave biopsies for suspected melanoma due to risk of understaging 1. The UK guidelines similarly state diagnostic shave biopsies should not be performed 1. The guideline recommendations take precedence over individual retrospective studies when patient safety and accurate staging are at stake.