Derm Cases · Dermatology / Paediatrics / Neurosurgery / Plastic surgery
OSCE — giant congenital melanocytic naevus: size risk, melanoma, and NCM MRI
An 8-minute OSCE station on congenital melanocytic naevus size classification, melanoma risk in giant CMN, neurocutaneous melanocytosis screening indications, and when to biopsy or image.
On this page
Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on congenital melanocytic naevus size classification, melanoma risk in giant CMN, neurocutaneous melanocytosis screening indications, and when to biopsy or image.
Brief (to candidate)
A newborn has a large dark plaque covering much of the back (projected adult size ≥20 cm) with numerous satellite naevi. Parents ask about "removal now" and cancer risk. You have 8 minutes to classify, counsel melanoma/NCM risk, and plan MRI and surveillance.
Candidate instructions
- Define CMN and size classes (small/medium/large-giant).
- State approximate melanoma risk emphasis for giant CMN.
- Identify NCM high-risk features and MRI timing.
- Describe when to biopsy within a CMN.
- Outline multidisciplinary management (not automatic radical newborn excision of all giant lesions).
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Definition / genetics | Melanocytic naevus present at birth/early weeks; mosaic RAS-MAPK (NRAS common in giant CMN)[5][6] |
| Size classification | Projected adult size: small <1.5 cm; medium 1.5–19.9 cm; large/giant ≥20 cm (or large % BSA); satellites increase systemic concern |
| Melanoma risk | Highest in giant CMN; risk often quoted in the 5–15% lifetime range in classic teaching (varies by series); may arise deep and in childhood — not only adult surface change; full-thickness biopsy of suspicious nodules[2][4] |
| NCM screening | Posterior axial giant CMN + many satellites → risk of neurocutaneous melanocytosis; MRI brain and spine ideally in first months of life; neurology if seizures/raised ICP/developmental issues[2][3] |
| Surveillance / surgery | Serial photography/exam; plastic surgery/derm for staged excision or observation depending on size, site, psychosocial needs — not one-size emergency total removal in all newborns |
| Other | Palpebral involvement → ophthalmology; change (nodule, ulcer, colour shift, bleeding) → urgent specialist review |
| Communication | Honest risk counselling without fatalism; safety-net neurologic symptoms |
Model key actions
- Classify as giant CMN with satellites — highest risk category for melanoma/NCM counselling.[2]
- Arrange early MRI neuraxis for NCM risk stratification.[3]
- Biopsy new nodules/change; plan long-term multidisciplinary follow-up.[4]
Common errors
- Treating all CMN as identical melanoma risk.
- Missing NCM MRI indications in axial giant + satellites.
- Superficial shave of deep concerning nodule.
- Promising that complete excision eliminates all neurologic risk if NCM already present.
References5ShowHide
- [2]Viana AC, Gontijo B, Bittencourt FV. Giant congenital melanocytic nevus. Anais Brasileiros de Dermatologia, 2013.PMID 24474093
- [3]Ruth J. Congenital melanocytic nevus syndrome: An association between congenital melanocytic nevi and neurological abnormalities. Seminars in pediatric neurology, 2024.PMID 39389659
- [4]Alos L, Carrasco A, Teixidó C, et al. Melanoma on congenital melanocytic nevi. Pathology, research and practice, 2024.PMID 38518732
- [5]Zayour M, Lazova R. Congenital melanocytic nevi. Clinics in laboratory medicine, 2011.PMID 21549240
- [6]Aimaier R, Chung M, Zhu H, et al. Spatiotemporal expression of NRAS and occurrence of giant congenital melanocytic nevi. Experimental dermatology, 2022.PMID 35020224