Can a 7 mm shave biopsy remove all of an in situ melanoma (lentigo maligna)?

Likelihood of Complete Removal with 7mm Shave Biopsy

A 7mm shave biopsy is unlikely to have completely removed a lentigo maligna, as these lesions characteristically extend laterally beyond clinically visible borders through subclinical spread of atypical melanocytes along the epidermis—a "field effect" that makes complete removal with narrow margins improbable. 1

Why Complete Removal is Unlikely

Subclinical Extension Pattern

• Lentigo maligna demonstrates extensive lateral spread of atypical melanocytes that are not clinically detectable, extending well beyond the visible pigmentation 1
• This subclinical extension is the primary reason why lentigo maligna has higher recurrence rates compared to other melanoma in situ subtypes 1
• Even surgical margins greater than 0.5 cm are often necessary to achieve histologically negative margins for lentigo maligna type melanoma in situ 1

Sampling Limitations of Shave Biopsy

• Shave biopsies create significant risk of underestimating the true extent and depth of melanoma lesions 2
• Initial incisional biopsies (including shave techniques) for lentigo maligna frequently suffer from sampling problems that make them non-representative of the whole lesion 1
• The American Academy of Dermatology specifically notes that shallow biopsies may miss focal microinvasion that could be present in areas not sampled 2

Probability Assessment

Most Likely Scenario

• The shave biopsy likely removed only a portion of the lentigo maligna, with residual atypical melanocytes extending beyond the 7mm biopsy site 1
• Studies show that even with wider surgical excisions, lentigo maligna commonly recurs due to incomplete removal of the lateral extension 1

Depth Considerations

• While a broad shave biopsy extending into deep papillary or superficial reticular dermis can provide adequate tissue sampling for diagnosis of lentigo maligna 1, the lateral extent is the critical issue
• A 7mm diameter represents relatively narrow sampling for a facial lentigo maligna, where lesions often measure several centimeters 3

Clinical Implications for Definitive Treatment

Re-excision Strategy

• The patient should undergo narrow-margin re-excision first to ensure accurate staging before definitive wide excision, as recommended by the American Academy of Dermatology 2
• This approach is critical because if microinvasion is found on deeper sampling, sentinel lymph node biopsy must be performed before wide excision 2

Margin Requirements

• Standard surgical margins for confirmed melanoma in situ are 0.5-1.0 cm measured clinically 1, 2
• For lentigo maligna specifically, margins greater than 0.5 cm are frequently required to achieve histologically negative margins 1
• Techniques for exhaustive histologic assessment of margins (such as staged excision or Mohs surgery) should be considered for facial locations 2

Key Pitfalls to Avoid

• Do not assume the shave biopsy was therapeutic—it should be considered purely diagnostic 1
• Do not proceed directly to wide excision without confirming the absence of invasion, as this could preclude sentinel lymph node biopsy if microinvasion is present 2
• The pathology report from re-excision must be reviewed by a pathologist experienced in pigmented lesions and must include Breslow thickness, ulceration status, mitotic rate, and margin status 1, 2