Correlation Between Surgical and Histologic Margins in Melanoma Wide Excision Specimens

Area of Science:

• Dermatology
• Surgical Oncology
• Pathology

Background:

• Wide surgical excision is the standard treatment for localized primary cutaneous melanomas.
• Narrow histologic margins are associated with an increased risk of local recurrence.
• The correlation between surgical and histologic margins is poorly documented.

Purpose of the Study:

• To document specimen shrinkage during formalin fixation.
• To predict the histologic margin using a precisely measured surgical margin in vivo.
• To assess the effects of clinicopathologic characteristics on specimen shrinkage and margin prediction.

Main Methods:

• Audit of 252 wide excision specimens for melanomas and other malignant skin tumors.
• Recorded measured surgical margin (in vivo), ex vivo specimen width, and histologic margins.
• Assessed effects of age, sex, BMI, tumor type, anatomic site, and visible tumor presence.

Main Results:

• Formalin-fixed specimens showed a mean shrinkage of 14% (R²=0.98), consistent across patient factors and lesion sites.
• Measured surgical margin was a poor predictor of the histologic margin (R²=0.55).
• Variability in margin prediction was not explained by patient factors, tumor subtype, or visible tumor presence (p>0.05).

Conclusions:

• A consistent 14% shrinkage rate was observed in wide excision specimens.
• A clinically useful 15% correction factor is proposed for fixation and shrinkage.
• Surgeon-measured excision margins are a poor predictor of final histologic margins.