Keratinocyte cancer

7.6 Protocol to manage incompletely resected basal cell carcinoma

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Case series conducted before 2000 suggested that a 4mm margin is required for most nodular basal cell carcinomas (BCC) to ensure complete histologic clearance.[1] 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.[2][3][4] These included prospective cohort study[2] and two retrospective cohort studies,[3][4] 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.[4] 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.[2] However, there was no control group.[2]

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.[3]

Available evidence shows that Incomplete excision does not always lead to recurrence.

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Evidence summary and recommendations

Evidence summary Level References
ALA-PDT versus re-excision

No significant difference in recurrence rates was found between ALA-PDT or re-excision.

III-3 [2]
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.

III-2 [3]
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.

III-2 [4]
Evidence-based recommendationQuestion mark transparent.png Grade
EBR 7.6.1. Incompletely excised basal cell carcinomas should be assessed and treatment selected on a case-by-case basis.
Evidence-based recommendationQuestion mark transparent.png Grade
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.

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.[3][4] High-risk tumours in high risk sites warrant further surgery, possibly including a wider excision or excision with a margin control technique.


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View Systematic review report SX4Systematic review report SX4

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  1. Wolf DJ, Zitelli JA. Surgical margins for basal cell carcinoma. Arch Dermatol 1987 Mar;123(3):340-4 Available from:
  2. 2.0 2.1 2.2 2.3 2.4 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 Available from:
  3. 3.0 3.1 3.2 3.3 3.4 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 Available from:
  4. 4.0 4.1 4.2 4.3 4.4 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 Available from:

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