Derm Cases · Dermatology / Pigmented lesions
OSCE — moles and special naevi: classification, dermoscopy patterns and biopsy thresholds
An 8-minute OSCE station on acquired vs congenital melanocytic naevi, special subtypes (Spitz, blue, halo), age-related dermoscopy patterns, ABCDE/ugly-duckling triage, and biopsy thresholds.
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Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on acquired vs congenital melanocytic naevi, special subtypes (Spitz, blue, halo), age-related dermoscopy patterns, ABCDE/ugly-duckling triage, and biopsy thresholds.
Brief (to candidate)
A 28-year-old woman requests mole review. She has multiple stable brown naevi, a pink hairless papule on a child’s arm (brought by her son), and a history of a large congenital naevus in a relative. She asks which moles are safe to leave and which need excision. You have 8 minutes to classify naevi, apply triage rules, and set biopsy/surveillance thresholds.
[5]Candidate instructions
- Classify acquired naevi (junctional / compound / intradermal) and maturation concept.
- Outline dermoscopy patterns by age (globular / reticular / homogeneous).
- Apply ABCDE and ugly-duckling rules.
- Discuss Spitz, blue, and halo naevi management concepts.
- Address congenital melanocytic naevus size risk and when MRI/surveillance matters.
- State preferred biopsy approach when melanoma cannot be excluded.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Classification | Acquired (junctional → compound → intradermal maturation); congenital (small/medium/large-giant); special types (Spitz, blue, halo/Sutton, dysplastic)[4] |
| Dermoscopy patterns | Age-linked benign patterns (often globular in children, reticular young adults, homogeneous older adults); chaos/clues or atypical features prompt action rather than indefinite observation |
| Triage rules | ABCDE + ugly duckling for changing or outlier lesions; photography/serial monitoring for stable typical naevi |
| Spitz concept | Pink-red dome-shaped papule in child = Spitz spectrum; excisional biopsy preferred when diagnosis uncertain because Spitzoid melanoma must be excluded; histopathology may need expert review[1][6] |
| Congenital naevi | Risk rises with size (large/giant CMN); melanoma can arise within CMN; giant CMN — consider neurocutaneous melanosis risk and imaging/neurology pathway per size and symptoms; shared decision on excision vs surveillance[3][5] |
| Biopsy / genetics note | Full-thickness excisional biopsy with narrow margins preferred for suspicious pigmented lesions; multiple atypical naevi + family melanoma history → consider hereditary melanoma counselling (e.g. CDKN2A context)[2] |
| Communication | Reassure most moles are benign; teach self-skin exam and urgent return for change |
Model key actions
- Reassure regarding stable typical acquired naevi; escalate ugly duckling / ABCDE lesions.[4]
- Manage suspected Spitz with complete excision rather than partial shave when feasible.[1][6]
- Risk-stratify congenital naevi by size and counsel surveillance/specialist input.[5]
Common errors
- Excising every mole cosmetically without diagnostic criteria.
- Partial superficial sampling of a changing pigmented lesion.
- Dismissing childhood pink papules without considering Spitz spectrum.
- Ignoring size-based risk in giant congenital naevi.
- Missing family-history clues for hereditary melanoma predisposition.
References6ShowHide
- [1]Brown A, Sawyer JD, Neumeister MW. Spitz Nevus: Review and Update. Clinics in plastic surgery, 2021.PMID 34503728
- [2]Toussi A, Mans N, Welborn J, et al. Germline mutations predisposing to melanoma. Journal of cutaneous pathology, 2020.PMID 32249949
- [3]Alos L, Carrasco A, Teixidó C, et al. Melanoma on congenital melanocytic nevi. Pathology, research and practice, 2024.PMID 38518732
- [4]Yeh I. Melanocytic naevi, melanocytomas and emerging concepts. Pathology, 2023.PMID 36642570
- [5]Mologousis MA, Tsai SY, Tissera KA, et al. Updates in the Management of Congenital Melanocytic Nevi. Children (Basel, Switzerland), 2024.PMID 38255375
- [6]Yeh I, Busam KJ. Spitz melanocytic tumours - a review. Histopathology, 2022.PMID 34958498