Do infiltrative basal cell carcinomas (BCC) require Mohs surgery?

Mohs Surgery for Infiltrative Basal Cell Carcinoma

Yes, infiltrative basal cell carcinomas require Mohs micrographic surgery (MMS) as the treatment of choice due to their aggressive growth pattern, unpredictable subclinical extension, and significantly higher recurrence rates with standard excision. 1

Why Infiltrative BCC is High-Risk

Infiltrative BCC represents an aggressive histologic subtype that behaves fundamentally differently from nodular or superficial variants:

• Infiltrative BCCs extend significantly wider and deeper than clinically apparent, making standard excision with predetermined margins inadequate for complete removal 2, 3
• The subclinical tumor spread is asymmetrical and unpredictable, requiring comprehensive margin assessment that only MMS can provide 2
• Infiltrative subtypes are classified as "aggressive growth patterns" alongside micronodular, sclerosing, and morpheaform variants, all of which carry higher recurrence risk 1
• These tumors are significantly more destructive and difficult to eradicate than nodular BCC of similar clinical size, requiring more surgical stages and greater tissue removal 2, 3

Evidence Supporting MMS for Infiltrative BCC

The guideline consensus is unequivocal:

• The American Academy of Dermatology explicitly recommends MMS for high-risk BCC, which includes all aggressive histologic subtypes like infiltrative BCC 1
• MMS achieves 5-year cure rates of 99% for primary BCC and 94.4% for recurrent disease, far superior to standard excision 1
• Standard excision of high-risk tumors without complete margin assessment carries substantial risk - one study showed 26.8% recurrence with positive margins versus 5.9% with negative margins 1
• A 2020 study comparing MMS versus conventional excision for high-risk head and neck BCCs found 3.1% recurrence with MMS versus 14% with traditional surgery (P < .00001) 4

Why Standard Excision is Inadequate

Standard "bread loaf" histologic sectioning examines only 1-2% of the surgical margin, missing the covert infiltrative extensions characteristic of this subtype:

• Infiltrative BCC requires wider peripheral margins (5-10mm or more) even with standard excision, but even these margins may be insufficient without complete margin control 1
• The British Journal of Dermatology guidelines state that recurrent tumors, especially on the face, are at high risk of further recurrence following surgical excision even with wide surgical margins 1
• Strong caution is advised when selecting treatment without complete margin assessment for high-risk tumors 1

Clinical Algorithm for Infiltrative BCC

When infiltrative histology is confirmed on biopsy:

1. Refer for MMS immediately - this is the standard of care for aggressive histologic subtypes 1
2. If MMS is unavailable, consider standard excision with frozen section control and wide margins (minimum 5-10mm), but understand this is a compromise with higher recurrence risk 1
3. Never use curettage and electrodesiccation - this technique is absolutely contraindicated for aggressive histologic subtypes, with reported recurrence rates of 19-27% even when mistakenly used 1, 5
4. Location matters - facial infiltrative BCCs are particularly high-risk and MMS becomes even more critical for tissue preservation and margin control 1, 4

Critical Pitfalls to Avoid

• Do not treat infiltrative BCC as "just another BCC" - the infiltrative subtype is fundamentally more aggressive and requires specialized surgical approach 2, 3
• Do not rely on clinical margins - infiltrative growth is duplicitous and extends far beyond what is visible or palpable 2
• Do not use destructive techniques (C&E, cryotherapy) that provide no margin assessment for aggressive subtypes 1, 5
• Do not delay referral for MMS - incomplete initial excision of infiltrative BCC makes subsequent cure more difficult, especially if flaps or grafts were used for reconstruction 1