Derm Cases · Dermatology / Dermatopathology
OSCE — dense dermal infiltrate: separate pseudolymphoma, CTCL, and LCH pathways
An 8-minute OSCE on pattern diagnosis of lymphoid/histiocytic infiltrates, IHC lineage panels, WHO-EORTC language, clonality pitfalls, and urgent staging for multisystem LCH or aggressive lymphoma.
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Target exams
NEET-PGINICETUSMLEPLABMRCPFRCDerm
Prompt
An 8-minute OSCE on pattern diagnosis of lymphoid/histiocytic infiltrates, IHC lineage panels, WHO-EORTC language, clonality pitfalls, and urgent staging for multisystem LCH or aggressive lymphoma.
Brief (to candidate)
You receive a skin biopsy report: “dense dermal lymphoid infiltrate, atypical cells present.” The patient is a middle-aged adult with chronic patches and a new nodule. In 8 minutes, structure a clinicopathologic approach, request the right IHC, and state when to stage systemically.
Candidate instructions
- Describe architectural patterns you would look for on H&E.
- Choose a lineage IHC panel (T vs B vs histiocyte).
- Explain pseudolymphoma vs lymphoma decision points and clonality limits.
- Name WHO-EORTC entities that change management (e.g. leg-type CBCL).
- State red flags requiring haemato-oncology/paediatric oncology staging (SS features, aggressive CBCL, multisystem LCH).
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Pattern | Mentions epidermotropic/band-like, nodular, diffuse, folliculotropic patterns |
| IHC | CD3/CD20 fork; CD30 when large-cell LPD; CD1a/langerin if histiocytic |
| Pseudolymphoma | Reactive triggers; mixed cells; clonality not absolute[2] |
| Classification | Uses WHO-EORTC language; flags aggressive leg-type CBCL[1][4] |
| Histiocyte pearl | LCH markers or RDD emperipolesis if asked[3][5] |
| Safety | Does not start multiagent chemo from one vague report without correlation |
| Communication | Explains need for clinical photos, nodes exam, possible re-biopsy |
Model key actions
- Treat the report as a question, not a final disease label.
- Integrate skin exam + nodes + drug/exposure history.
- Escalate staging when behaviour is aggressive or histiocytosis is multisystem.
Common errors
- Equating any dense infiltrate with lymphoma.
- Relying on clonality alone.
- Missing paediatric LCH systemic risk.
- Excising only and discharging aggressive leg tumours without staging.
References5ShowHide
- [1]Willemze R, Cerroni L, Kempf W, et al. The 2018 update of the WHO-EORTC classification for primary cutaneous lymphomas. Blood, 2019.PMID 30635287
- [2]Mitteldorf C, Kempf W. Cutaneous pseudolymphoma—A review on the spectrum and a proposal for a new classification. Journal of Cutaneous Pathology, 2020.PMID 31237707
- [3]Krooks J, Minkov M, Weatherall AG. Langerhans cell histiocytosis in children: History, classification, pathobiology, clinical manifestations, and prognosis. Journal of the American Academy of Dermatology, 2018.PMID 29754885
- [4]Goyal A, LeBlanc RE, Carter JB. Cutaneous B-Cell Lymphoma. Hematology/Oncology Clinics of North America, 2019.PMID 30497672
- [5]Bruce-Brand C, Schneider JW, Schubert P. Rosai-Dorfman disease: an overview. Journal of Clinical Pathology, 2020.PMID 32591351