Case series conducted before 2000 suggested that a 4mm margin is required for most nodular basal cell carcinomas (BCC) to ensure complete histologic clearance. However, a 4mm margin may be excessive for some BCCs and insufficient in others.
The report of a positive margin does not indicate that tumour persists or the recurrence is inevitable. Incomplete deep margins may carry a worse prognosis than incomplete lateral margins.
Following a report of incomplete or close margins, re-excision to achieve clearance is generally considered necessary for BCCs with high-risk features (unfavourable anatomical site, type or histologic features associated with poorer prognosis).
Systematic review evidence
What should be the protocol to manage incompletely resected basal cell carcinoma?
A systematic review was undertaken to answer this clinical question. The search strategy, inclusion and exclusion criteria, and quality assessment are described in detail in the Technical report.
Three studies reported relevant outcomes for incompletely resected BCCs after comparing two or more treatment interventions. These included prospective cohort study and two retrospective cohort studies, all with a high risk of bias.
Treatment modalities included secondary surgical excision (re-excision), aminolevulinic acid-photodynamic therapy (ALA-PDT), electrodessication and curettage (EDC), topical imiquimod, topical 5-flourouracil and topical liquid nitrogen.
All three studies reported recurrence rates. A US retrospective cohort study in which patients received various treatments (including EDC, topical imiquimod, 5-flourouracil, liquid nitrogen) or observation only found that among incompletely excised low-risk tumours, recurrence was more likely in tumours of the head and neck, larger tumours and superficial subtype of BCC after a mean follow-up interval of 40 months. The findings of this study supported a non-surgical approach to some recurrences, but the effect of this was not analysed.
The findings of a Chinese prospective cohort study suggest that ALA-PDT can possibly cure residual tumour, based on observed outcomes for patients with low grade lesions misdiagnosed as naevi, where the intention of initial excision was not curative. However, there was no control group.
A Brazilian retrospective cohort study comparing re-excision with observation found that recurrence was not inevitable with incomplete margins, and over 50% did not recur.
Available evidence shows that Incomplete excision does not always lead to recurrence.
Evidence summary and recommendations
| ALA-PDT versus re-excision
No significant difference in recurrence rates was found between ALA-PDT or re-excision.
| Observation versus re-excision
More tumours recurred after re-excision than observation. In the one study that reported this comparison, more tumours recurred after re-excision (50%) than observation (15%), in a small cohort of patients.
| Observation versus EDC, topical imiquimod, topical 5-flourouracil, liquid nitrogen, dual treatment
Incompletely resected BCCs treated with topical imiquimod were significantly more likely to recur than incompletely resected BCCs monitored with observation only.
|EBR 7.6.1. Incompletely excised basal cell carcinomas should be assessed and treatment selected on a case-by-case basis.||C|
|EBR 7.6.2. Incompletely excised basal cell carcinomas that have high-risk features, or occur in high-risk anatomical sites, should be re-excised, where possible.||C|
Notes on these recommendations
The available evidence supports an individualised approach in the management of incompletely resected BCCs at low-risk sites with low-risk histopathology. High-risk tumours in high risk sites warrant further surgery, possibly including a wider excision or excision with a margin control technique.
- Surgical treatment – Introduction
- Considerations before selecting a surgical treatment modality
- Optimal primary excision techniques:
- Post-surgical care and interpretation of the pathology report
- Protocol to manage rapidly growing tumours
- Criteria for choosing Mohs micrographic surgery in preference to other surgical techniques
- Surgical management of advanced cutaneous squamous cell carcinoma
- Surgical treatment – Health system implications and discussion
|PICO question SX4||Evidence statement form SX4
|Systematic review report SX4|
- Wolf DJ, Zitelli JA. Surgical margins for basal cell carcinoma. Arch Dermatol 1987 Mar;123(3):340-4 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/3813602.
- Bu W, Zhang M, Zhang Q, Yuan C, Chen X, Fang F. Preliminary results of comparative study for subsequent photodynamic therapy versus secondary excision after primary excision for treating basal cell carcinoma. Photodiagnosis Photodyn Ther 2017 Mar;17:134-137 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27888160.
- Lara F, Santamaría JR, Garbers LE. Recurrence rate of basal cell carcinoma with positive histopathological margins and related risk factors. An Bras Dermatol 2017 Jan;92(1):58-62 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/28225958.
- Rieger KE, Linos E, Egbert BM, Swetter SM. Recurrence rates associated with incompletely excised low-risk nonmelanoma skin cancer. J Cutan Pathol 2010 Jan;37(1):59-67 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/19615009.