Derm Cases · Dermatology / Dermatopathology / Skin cancer MDT
OSCE — melanocytic pathology: biopsy, naevus vs melanoma criteria, report elements
An 8-minute OSCE on correct melanoma biopsy technique, architectural criteria distinguishing naevus from melanoma, essential AJCC pathology report elements, PRAME as ancillary only, and MPATH-Dx-style action for ambiguous lesions.
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Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE on correct melanoma biopsy technique, architectural criteria distinguishing naevus from melanoma, essential AJCC pathology report elements, PRAME as ancillary only, and MPATH-Dx-style action for ambiguous lesions.
Brief (to candidate)
You are in a pigmented lesion clinic. A 48-year-old has an irregular back lesion. The trainee pathologist asks how you will biopsy it and what you need on the report if melanoma is confirmed. In 8 minutes, set out a safe clinicopathologic plan.
[2]Candidate instructions
- State preferred biopsy technique and why shave understages.
- List architecture-first criteria naevus vs melanoma.
- Name Breslow measurement landmarks and ulceration importance.
- Mention PRAME as ancillary only.
- Note MPATH-Dx/expert review for ambiguous or adult Spitzoid lesions.
- Link invasive melanoma to WLE ± SLNB pathway (staging principles).
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Biopsy | Prefers full-thickness excisional biopsy with narrow margins; flags incomplete superficial shave risk for Breslow understaging[1][2] |
| Criteria | Names symmetry/maturation vs asymmetry, pagetoid scatter, deep mitoses, sheet-like growth |
| Report elements | Breslow from granular layer/ulcer base; ulceration; margins; subtype/adverse features[1][2] |
| Ancillary | PRAME/IHC support diagnosis but do not replace morphology[4] |
| Grey zone | Ambiguous/adult Spitzoid → complete excision + specialist review; MPATH-Dx class language for action[3][5] |
| Next steps | Invasive melanoma → WLE margins concept ± SLNB discussion per stage |
| Communication | Clear plan, photography, follow-up for scar and new lesions |
Model key actions
- Excisional full-thickness biopsy first when melanoma is realistic.[2]
- Architecture constellation over single-feature diagnosis.
- AJCC-ready report elements for T category.[1]
- Do not treat PRAME as standalone proof of melanoma.[4]
Common errors
- Planning shave-only for obvious melanoma.
- Observing a transected atypical base because “report said possible naevus.”
- Equating childhood Spitz naevus risk with adult Spitzoid lesions.
- Ordering SLNB before histologic confirmation of invasive melanoma.
References5ShowHide
- [1]Gershenwald JE, Scolyer RA. Melanoma Staging: American Joint Committee on Cancer (AJCC) 8th Edition and Beyond. Annals of Surgical Oncology, 2018.PMID 29850954
- [2]Scolyer RA, Rawson RV, Gershenwald JE, et al. Melanoma pathology reporting and staging. Modern Pathology, 2020.PMID 31758078
- [3]Barnhill RL, Elder DE, Piepkorn MW, et al. Revision of the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis Classification Schema for Melanocytic Lesions: A Consensus Statement. JAMA Network Open, 2023.PMID 36630138
- [4]Lezcano C, Jungbluth AA, Nehal KS, et al. PRAME Expression in Melanocytic Tumors. American Journal of Surgical Pathology, 2018.PMID 30045064
- [5]Yeh I, Busam KJ. Spitz melanocytic tumours — a review. Histopathology, 2022.PMID 34958498