What are the recommended depth and width for excising squamous cell carcinoma on the leg?

Excision Margins for Squamous Cell Carcinoma on the Leg

For low-risk squamous cell carcinoma on the leg, excise with a 4-6 mm lateral margin extending to the mid-subcutaneous adipose tissue depth, with histologic margin assessment. 1

Lateral (Width) Margins

• 4-6 mm clinical margin of uninvolved skin around the tumor and any surrounding erythema is recommended for low-risk primary cutaneous SCC 1, 2
• This margin achieves approximately 95% clearance rates based on Mohs micrographic surgery data showing that 4 mm margins clear most low-risk lesions 1
• The leg (including pretibial area) is not classified as a high-risk anatomical location, unlike central face, ears, or genitalia 1
• Any peripheral rim of erythema must be included in what is considered the tumor margin—a common pitfall is underestimating clinical tumor extent 2

Depth of Excision

• Extend to the mid-subcutaneous adipose tissue with histologic margin assessment 1, 2
• This depth is critical, as 94% of incomplete excisions involve the deep margin rather than lateral margins 3
• Failing to achieve adequate depth is a major cause of incomplete excision despite appropriate lateral margins 3

Risk Stratification Considerations

Low-Risk Features (4-6 mm margins appropriate):

• Well-differentiated histology 2
• Tumor diameter <2 cm 1, 4
• Primary (not recurrent) tumor 1
• No perineural invasion 4
• Depth ≤2 mm 4

High-Risk Features (consider wider margins or Mohs surgery):

• Poorly differentiated histology 1, 4
• Tumor diameter ≥2 cm (requires at least 6 mm margins) 1
• Depth >2 mm 4
• Recurrent tumor 4
• Perineural invasion 4
• Immunosuppressed patients 4

Surgical Technique Recommendations

• Use marker sutures for specimen orientation to facilitate histopathologic evaluation 1
• Mount/pin the specimen to a board and photograph before sampling for optimal margin assessment 1
• Perform "bread loaf" histopathologic sectioning with assessment of both lateral and deep margins 1
• If margins are positive, the histopathology report should specify which margin is involved 1

Closure Considerations

• For low-risk tumors, primary closure, skin graft, or healing by secondary intention are acceptable 1
• If significant tissue rearrangement is required, delay closure until negative histologic margins are confirmed 1
• This prevents the need for re-excision through a complex reconstruction 1

Alternative Approach for High-Risk Tumors

• Mohs micrographic surgery is recommended for high-risk SCC with 5-year recurrence rates of only 3.1% compared to 8.1% for standard excision 1
• Standard excision may be considered for select high-risk tumors, but strong caution is advised when treating high-risk disease without complete margin assessment 1
• For tumors >2 cm or poorly differentiated lesions, Mohs surgery shows significantly lower recurrence rates (25.2% vs 41.7% for standard excision) 1

Critical Pitfalls to Avoid

• Inadequate depth: Most incomplete excisions fail at the deep margin, not laterally 3
• Underestimating clinical extent: Include all erythema in the presumed tumor 2
• Inadequate margin assessment: Ensure histologic confirmation of clear margins before complex reconstruction 1
• Treating high-risk features as low-risk: Recurrent tumors, poor differentiation, and depth >2 mm require more aggressive approaches 1, 4