Melanoma in the ST3 Plastics Interview
How to answer a melanoma scenario in the ST3 Plastic Surgery interview: excision biopsy, Breslow-based margins, sentinel node criteria, and the skin cancer MDT.
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The changing mole is the ST3 plastics station where pathway knowledge is the skill being examined: biopsy done the right way, margins scaled to Breslow thickness, sentinel node criteria, and the MDT holding it all together.
How the scenario tends to open
A typical stem: a young woman in clinic with a mole on her forearm that has grown and changed colour over months. The examiner walks the pathway with you: assessment, biopsy, what you want from pathology, then staging, definitive margins, and follow-up — often with a concrete histology twist to stage in your head.
The approach that scores
Assess like a skin oncologist: ABCDE for the lesion (asymmetry, border, colour, diameter, evolution), risk factors (sunburns, skin type, personal or family history, immunosuppression), regional lymph node basins, and a full skin check for other lesions. Dermatoscopy strengthens the answer.
Then the sentence that anchors the biopsy: a suspected melanoma gets a complete excision biopsy with a 2 mm margin and a cuff of fat — never a shave or punch — orientated for the definitive operation, and sent urgently. From pathology you want Breslow thickness, ulceration, mitotic rate, and margins; Breslow drives everything downstream.
- Confirmed melanoma goes to the specialist skin cancer MDT, managed per BAD guidelines and AJCC (8th edition) staging.
- Wide local excision margins scale with Breslow thickness — from 5 mm for in-situ disease up to 2–3 cm for the thickest tumours; quote the banded scheme rather than a single number.
- Sentinel lymph node biopsy is offered from pT1b — a staging procedure, not a therapeutic one, and a positive node returns to the MDT for surveillance-versus-surgery and adjuvant discussions.
- Palpable nodes at any point get ultrasound-guided FNA, not open biopsy.
- Complete the picture: staged follow-up with skin surveillance, sun-protection and self-examination education, and awareness that BRAF testing and adjuvant immunotherapy enter from the mid-stages.
Where candidates lose marks
The classic errors are procedural: offering a shave or punch biopsy of a suspected melanoma, quoting one flat excision margin for every depth, or skipping the MDT as if margins were a solo decision. When the twist lands — say, a Breslow of 1.4 mm without ulceration — the examiner wants you to place it (pT2a), give its margin band (1–2 cm), and recognise it qualifies for sentinel node biopsy. Practising a few staging examples aloud pays for itself.
Rehearse it
Reading about melanoma is the easy half. Rehearse this exact scenario out loud, on the clock, with an AI examiner — this scenario is in Reviva’s library, with feedback marked the way the panel marks. Or start with the wider format in the st3 plastics clinical station guide.
Frequently asked questions
- Why is excision biopsy required for suspected melanoma?
- Because partial sampling (shave or punch) can miss the deepest point of the tumour — and Breslow thickness, measured from the whole lesion, determines staging, margins, and sentinel node eligibility.
- What margins does a melanoma need?
- Wide local excision margins scale with Breslow thickness: 5 mm for in-situ disease, rising in bands to 2–3 cm for the thickest tumours, per BAD guidance discussed at the skin MDT.
- Who qualifies for sentinel lymph node biopsy?
- From pT1b upwards — including 0.8–1.0 mm with ulceration, or over 1 mm regardless. It is a staging investigation; a positive result goes back to the MDT for staging imaging and the surveillance-versus-completion discussion.
Sources. Grounded in BAD melanoma guidance and AJCC 8th-edition staging (excision biopsy technique, Breslow-scaled margins, SLNB thresholds, MDT pathways) as rehearsed in Reviva’s ST3 plastics scenario. Educational only.