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Factors Influencing Margin Clearance and Number of Stages of Mohs Surgery in BCC Management


A recent study offers a comprehensive analysis of practice patterns and patient characteristics in different clinical settings.

Basal cell carcinoma on a patient's ear | Image Credit: © plazaccameraman - stock.adobe.com

Image Credit: © plazaccameraman - stock.adobe.com

Mohs micrographic surgery (MMS) stands as the gold standard for the treatment of basal cell carcinoma (BCC), offering high cure rates while preserving healthy tissue. However, the influence of patient demographics and tumor characteristics on surgical outcomes, such as clearance margins and the number of MMS stages required, remains under-explored. A recent retrospective study involving 7651 patients sheds light on how relationships involving patient age, clearance margins, high-risk BCC subtypes, MMS stages, and types of practice intertwine.1

Study Overview 

The primary aim of this study was to evaluate how patient demographics and BCC subtypes affect the size of the defect needed to clear BCC and the number of MMS stages required. Conducted across both academic centers and private practices, the study offers a comprehensive analysis of practice patterns and patient characteristics in different clinical settings.

Top 3 Findings

1. Age and Clearance Margins: The study found that clearance margins increased with patient age. Specifically, each additional year of age was associated with a 0.1 mm increase in clearance margin at academic centers and a 0.04 mm increase at private practices. This finding underscores the importance of considering patient age when planning MMS, as older patients may require larger margins to achieve complete tumor clearance. “Several studies have also shown larger subclinical spread with older age, which is attributed to increased cumulative sun exposure and skin damage with age; however, the relative contribution of age to the risk of subclinical spread has not been quantified,” investigators wrote.2-3

2. High-Risk BCC and MMS Stages: High-risk BCC subtypes, including morpheaform, infiltrative, and micronodular, were associated with an increased number of MMS stages. At academic centers, high-risk BCCs required an average of 0.25 more stages compared to low-risk BCCs. This highlights the need for careful preoperative assessment and potentially more extensive surgical planning for high-risk cases.1

3. Differences Between Academic Centers and Private Practices: The study revealed notable differences in practice patterns between academic centers and private practices. Patients treated at academic centers generally had larger clearance margins (7 mm vs. 4 mm) and required more MMS stages (median of 2 vs. 1) compared to those treated at private practices. These differences may reflect variations in patient populations, tumor characteristics, and surgical approaches. “Private practices had fewer male patients and performed MMS on more superficial BCC, in addition to more morpheaform/fibrosing/sclerosing/invasive/infiltrative or basosquamous subtypes compared to academic centers. There were also some notable differences in practice patterns, as evidenced by the fewer MMS layers required to achieve clearance in private practice settings,” investigators wrote.1

Clinical Considerations

For dermatology clinicians, these findings have several important implications. Understanding that older patients may require larger clearance margins can help clinicians better plan and execute MMS. This is crucial for minimizing recurrence while preserving as much healthy tissue as possible. Identifying high-risk BCC subtypes preoperatively can prepare clinicians for potentially more complex surgeries requiring additional stages. This can improve patient counseling and surgical planning. Dermatology clinicians in private practice should be aware of the differences in practice patterns compared to academic centers. This awareness can aid in setting realistic expectations for patients regarding the extent of surgery and recovery.

“In an era when practice patterns benchmarked to national colleagues are crucial, it is important to consider that patient factors (age, gender) and tumor factors (BCC subtype) may also play an important role in predicting the clearance of the tumor and the required number of MMS stages to achieve it,” investigators concluded.


  1. Daniel VT, Azzolino V, Abraham M, et al. Factors influencing margin clearance and the number of stages of Mohs micrographic surgery in basal cell carcinoma: a retrospective chart review. Cancers. 2024; 16(13):2380. https://doi.org/10.3390/cancers16132380
  2. Santos-Arroyo A, Carrasquillo OY, Cardona R, Sánchez JL, Valentín-Nogueras S. Non-Melanoma Skin Cancer Tumor's Characteristics and Histologic Subtype as a Predictor for Subclinical Spread and Number of Mohs Stages required to Achieve Tumor-Free Margins. P R Health Sci J. 2019;38(1):40-45.
  3. Greywal T, Goldenberg A, Eimpunth S, Jiang SB. Key characteristics of basal cell carcinoma with large subclinical extension. J Eur Acad Dermatol Venereol. 2020;34(3):485-490. doi:10.1111/jdv.15884
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