Excision margins and elliptical excision

Meet the patient

A 62-year-old gardener has a pearly, telangiectatic nodule on the side of his nose. The shave biopsy confirms a well-differentiated basal cell carcinoma. The plan writes itself on the skin in marker: a 4 mm margin around the lesion, a fusiform ellipse three times as long as it is wide aligned to the nasolabial crease, and a layered closure — unless a high-risk feature sends him to Mohs instead.[1]

Two questions decide every ellipse: what margin does this disease need? (the histology and the risk features answer that) and how do I close the hole without distorting a free margin? (the site and the RSTLs answer that). Get those two right and the rest is technique.[1]

Two margins that must never be confused

Clinical margin and histologic margin are not the same thing, and conflating them is the commonest conceptual error in skin surgery.[7]

• Clinical surgical margin — the distance you measure on living skin from the visible (or dermoscopically mapped) edge of the lesion to your incision. This is the number you mark before cutting.
• Histologic margin — whether tumour actually reaches the inked peripheral or deep edge on the pathology slides. This is the number the pathologist reports days later.[7]

The gap between them is bread-loaf sectioning. Standard vertical sectioning examines representative slices — typically less than one percent of the true peripheral margin — so a report of clear margins samples only a fraction of the edge. Mohs micrographic surgery is the exception: it examines the entire peripheral and deep margin in staged horizontal sections, which is why it is the gold standard for tissue-sparing, high-risk facial tumours.[1]

The classic trap: equating a pathology report of clear margins after bread-loafing with complete histologic clearance. In a high-risk tumour, correlate clinically — and escalate to Mohs when the clearance must be guaranteed.[7]

The geometry — why three-to-one and why along the RSTLs

A short, wide defect shoves excess tissue into conical standing cones — dog ears — at each apex. Lengthen the ellipse to roughly three times its width and that excess redistributes so the apices close flat; that is the classic three-to-one teaching ratio, modified by site and skin elasticity.[8]

Layered closure places absorbable sutures in the dermis and subcutis to obliterate dead space and take the tension off the epidermis, then fine epidermal or subcuticular sutures finish the alignment. Undermine just enough to mobilise the edges without devascularising the tips.[1]

Consultant confession: a small residual dog ear is better left alone than chased with ever-longer extensions. Many regress with time, and the regression varies by site — face more, back less.[9]

Orient every specimen with a suture or ink so the pathologist can localise any positive margin; without orientation, a positive margin is an unlocalisable problem.[1]

The pattern of excision — match the intent to the lesion

Choose the excision pattern from the intent: diagnostic, therapeutic, wide-local, or margin-controlled. Each has a different job.[1]

[1]

Melanoma — the Breslow ladder

Melanoma margins are dictated by Breslow thickness, and no wide local excision should be planned without a reliable Breslow from an adequate biopsy. The AAD guidelines of care and the trial lineage that built the modern NCCN-style tables converge on the same ladder.[1][10]

[1]

Depth is taken to subcutaneous tissue appropriate to the site; anatomic constraints on a digit or the face may demand specialised surgical-oncology planning. Meta-analytic work continues to refine how much width is enough, but the board answer still starts from the thickness ladder.[2]

Basal cell carcinoma — about 4 mm for low-risk, Mohs for high-risk

For a well-defined, primary, low-risk BCC, a clinical margin of about 4 mm is the classic teaching figure, associated with high rates of histologic clearance in standard excision series.[5][3]

The moment a high-risk feature appears, the pathway leaves the simple ellipse. High-risk means the H-zone of the face, recurrent disease, poorly defined borders, aggressive histology (infiltrative or morpheaform), large size, or immunosuppression — and each one pushes toward Mohs or wider excision with careful reconstruction, not a minimal ellipse alone.[3]

The classic trap: closing a high-risk nasal or eyelid BCC with a tight 3 mm ellipse to keep the scar small trades a short scar today for deep recurrence tomorrow. Margin adequacy and method beat scar-length vanity.[1]

Squamous cell carcinoma — risk-stratify, and remember depth

Low-risk invasive SCC is planned at about 4 to 6 mm; high-risk SCC needs at least 6 mm or Mohs. The high-risk features are site (face, ear, lip), poor differentiation, deep invasion, perineural risk, recurrence, and immunosuppression.[4][6]

Everyone forgets depth. Peripheral width is only half the margin; the deep margin matters as much, and an inadequately deep excision recurs just as surely as an inadequately wide one. UK guidance is explicit that the best cut is the deepest.[6]

The face-off — ellipse versus the alternatives

The ellipse is the workhorse, but it is not always the right tool. Match the method to the tumour's risk and the site.[1]

[1]

The technique — stepwise elliptical excision

Run the ellipse in the same seven steps every time, and never force a closure that distorts a free margin.[1]

[1]

If linear closure would distort a free margin — eyelid, lip, alar rim, helical rim — or require extreme tension, redesign with a flap, a graft, or delayed reconstruction rather than forcing a short ellipse. Examiners expect early recognition and referral, not heroic linear closure under tension.[1]

Positive margins and special sites

A positive margin is not a single disease; management is context-dependent. Vertical sectioning can miss focal peripheral positivity between bread-loaf slices, so the report must specify peripheral versus deep involvement and the tumour type.[7]

Re-excise or move to Mohs for residual NMSC; convene multidisciplinary planning for melanoma; observe only in highly selected low-risk scenarios with informed consent — never as a default after incomplete high-risk clearance.[1]

Site-by-site adjustments that change the plan:[1]

• Face — prioritise RSTLs and aesthetic subunits; choose Mohs when risk is high.
• Acral or digit — functional margins and lower thresholds for specialist referral.
• Anticoagulated elderly — continue most anticoagulants for low-risk cutaneous surgery after individualised risk discussion, with meticulous haemostasis.
• Skin of colour — counsel on scar and dyspigmentation; keloid-prone sites need tension-minimising design.

[1]

Complications and follow-up

Complications split into early, late, and oncologic — and the oncologic one is the one that bites.[1]

[1]

Complete excision of low-risk NMSC with clear margins carries excellent local control; melanoma follow-up is stage-based. Give every patient a written plan for suture care, infection signs, and pathology-result review — never assume that no news means clear margins.[1]

Ward-round test

A shave biopsy of a pigmented lesion on the calf reports a 1.4 mm Breslow melanoma. What clinical margin do you plan, and what must you have before cutting?

The Breslow of 1.4 mm places this in the greater than 1.0 to 2.0 mm band, so the clinical margin is 1 to 2 cm, taken to subcutaneous tissue. Before cutting you must have a reliable Breslow from an adequate biopsy — never plan a melanoma WLE without complete microstaging, because the Breslow sets the margin, the sentinel-node decision, and the prognosis.[1][10]

A well-defined 6 mm BCC on the trunk of an immunocompetent patient. Margin, pattern, and closure?

This is a low-risk BCC: plan a clinical margin of about 4 mm, a therapeutic fusiform ellipse at roughly three-to-one along the RSTLs, and a layered closure. Bread-loafing samples only part of the margin, so read the pathology report in that light and re-excise if positive.[5][3]

The same BCC is on the ala of the nose, recurrent, with infiltrative histology. Why does the plan change?

These are high-risk features (H-zone face, recurrence, aggressive histology), and each pushes the pathway away from a simple ellipse toward Mohs micrographic surgery for 100 percent margin control and tissue sparing, with careful reconstruction. Closing a high-risk nasal BCC with a tight ellipse trades a short scar for deep recurrence.[3]

A pathology report after bread-loafing reads clear margins on a high-risk SCC. Is the tumour definitely completely excised?

No. Bread-loafing examines representative slices — less than one percent of the true peripheral margin — so clear margins sample only a fraction of the edge. In a high-risk tumour, correlate clinically and consider Mohs if guaranteed clearance matters; only Mohs examines the entire peripheral and deep margin.[7]

References

1. [1]Swetter SM, Tsao H, Bichakjian CK, et al. Guidelines of care for the management of primary cutaneous melanoma J Am Acad Dermatol, 2019.PMID 30392755
2. [2]Hanna S, Lo SN, Saw RP. Surgical excision margins in primary cutaneous melanoma: A systematic review and meta-analysis Eur J Surg Oncol, 2021.PMID 33722422
3. [3]Peris K, Fargnoli MC, Garbe C, et al. Diagnosis and treatment of basal cell carcinoma: European consensus-based interdisciplinary guidelines Eur J Cancer, 2019.PMID 31288208
4. [4]Stratigos A, Garbe C, Lebbe C, et al. Diagnosis and treatment of invasive squamous cell carcinoma of the skin: European consensus-based interdisciplinary guideline Eur J Cancer, 2015.PMID 26219687
5. [5]Quazi SJ, Aslam N, Saleem H, et al. Surgical Margin of Excision in Basal Cell Carcinoma: A Systematic Review of Literature Cureus, 2020.PMID 32821563
6. [6]Khan AA, Potter M, Cubitt JJ, et al. Guidelines for the excision of cutaneous squamous cell cancers in the United Kingdom: the best cut is the deepest J Plast Reconstr Aesthet Surg, 2013.PMID 23352886
7. [7]Weinstein MC, Brodell RT, Bordeaux J, et al. The art and science of surgical margins for the dermatopathologist Am J Dermatopathol, 2012.PMID 23000878
8. [8]Hudson-Peacock MJ, Lawrence CM. Comparison of wound closure by means of dog ear repair and elliptical excision J Am Acad Dermatol, 1995.PMID 7896954
9. [9]Jennings TA, Keane JC, Varma R, et al. Observation of Dog-Ear Regression by Anatomical Location Dermatol Surg, 2017.PMID 28930788
10. [10]Sharib J, Slingluff CL Jr, Beasley GM. Melanoma trials that defined surgical management: Overview of trials that established NCCN margin guidelines J Surg Oncol, 2022.PMID 34897715