Does squamous cell carcinoma in situ on the shin require Mohs surgery?

Squamous Cell Carcinoma In Situ on the Shin: Mohs Surgery is NOT Needed

Mohs micrographic surgery is not indicated for squamous cell carcinoma in situ (Bowen's disease) on the shin. Multiple other highly effective treatment options exist that are more appropriate for this location and clinical scenario.

Why Mohs is Not Recommended for Lower Leg SCC In Situ

The British Association of Dermatologists explicitly states that Mohs micrographic surgery may be indicated for digital SCC in situ (around the nail in particular) and for some cases of genital (especially penile) SCC in situ for its tissue-sparing benefits 1. Notably absent from these indications is lower leg disease, which represents the vast majority of shin lesions.

The evidence base for Mohs in SCC in situ is weak (Level D, expert opinion only) 1, and the procedure is considered overutilization for most primary SCC in situ in non-immunosuppressed patients 2.

Preferred Treatment Options for Shin Lesions

First-Line Recommendation: Photodynamic Therapy (PDT)

PDT is the highest-evidence treatment option (Level A recommendation) and may be of particular benefit for lesions on the lower leg 1. PDT achieves:

• Complete clearance rates of 88-100% at 3 months 1
• Superior cosmesis compared to cryotherapy and 5-fluorouracil 1
• Particularly advantageous for large lesions (>3 cm diameter) or difficult sites 1

Important caveat: Pain during treatment is common and patients should be counseled about this 1.

Alternative Effective Options

Curettage with cautery (Level C recommendation):

• Simple, inexpensive, safe and effective 1
• Preferable to cryotherapy in terms of pain, healing, and recurrence rate 1
• Success depends on operator skill 1

5-Fluorouracil 5% cream (Level B recommendation):

• More practical than surgery for large lesions, especially at potentially poor healing sites like the lower leg 1
• Less effective than PDT but not significantly different from cryotherapy 1

Observation with emollient use (Level D recommendation):

• In elderly patients with slowly progressive thin lesions, especially on the lower leg, observation is a reasonable option 1
• Regular use of emollient (especially containing urea) can reduce scaling 1

Critical Consideration: Lower Leg Wound Healing

Excisional procedures on the lower leg carry significant morbidity risk 1. The shin has:

• Poor healing properties due to suboptimal circulation 3
• Increased risk of surgical site complications 4
• Disadvantages with radiotherapy include particularly poor healing on the leg 1

This anatomic consideration strongly favors non-excisional treatments for shin lesions.

Clinical Outcomes Data

A retrospective study of 152 patients with lower extremity SCC in situ showed 4:

• Biopsy-proven recurrence rate: only 4.0%
• Clinical recurrence rate: only 1.3%
• Overall complication rate: 5.9%
• No significant difference in recurrence rates between local destruction, excision, and topical therapy

These low recurrence rates across treatment modalities demonstrate that Mohs surgery is unnecessary for achieving excellent outcomes 4.

When Excision Might Be Considered

If excision is chosen (Level C recommendation), it should be:

• For limited size lesions in suitable areas 1
• With consideration of cosmetic outcome, body site, healing properties, and vascularity 1
• Aware that lower-leg excision wounds may be associated with considerable morbidity 1

Standard excision with 4-6 mm margins is adequate for well-defined lesions <2 cm 1.

Bottom Line Algorithm

For SCC in situ on the shin:

1. First choice: PDT (especially if >3 cm or poor healing expected) 1
2. Alternative: Curettage with cautery or 5-fluorouracil 1
3. Elderly with thin lesions: Consider observation with emollient 1
4. Avoid: Mohs surgery (not indicated) 1, 2
5. Use caution with: Standard excision (healing concerns on lower leg) 1, 3