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Cutaneous T-cell lymphoma — mycosis fungoides and Sézary syndrome
Mycosis fungoides (MF) is a lymphoma of helper T cells (CD4) that homes to the skin and progresses slowly from patches to plaques to tumours; early stages are treated with skin-directed therapy, and Sézary syndrome is the leukaemic form with erythroderma.
Why it matters in the exam
The classic stem: an adult with itchy scaly patches in sun-protected areas (buttocks, hips) that have "not responded to steroids" for years, or erythroderma with lymph nodes and atypical cells in the blood. The exam tests the distinction from eczema and psoriasis, the need for repeated biopsies, staging, and stage-based treatment. Remember that the disease is more common in older men, that most patients are diagnosed at an early stage and do not die of it. On the other hand, late diagnosis is very common, because for many years the patient is treated for eczema or psoriasis without a biopsy, so any resistant scaly rash in covered areas should raise suspicion and lead to histology. For the exam, remember the terms patch, plaque, tumour and erythroderma, the TNMB staging and the difference between MF and Sézary syndrome, because many questions are built on that distinction and on choosing treatment by stage rather than by the intensity of the itch.
Key points
- MF is the most common cutaneous lymphoma, arises from helper T cells (CD4) and progresses slowly from patches to plaques to tumours.
- Lesions appear in sun-protected areas and mimic eczema and psoriasis, so repeated biopsies are sometimes needed.
- Staging is TNMB; in stage IA involvement is under 10% and prognosis is near normal.
- Early stages are treated with skin-directed therapy: steroids, mechlorethamine, NB-UVB or PUVA and local radiotherapy.
- Sézary syndrome includes erythroderma, nodes and atypical cells in the blood, and is treated with ECP and systemic therapy.
Summary table
| Stage or form | Findings | Prognosis | Treatment |
|---|---|---|---|
| IA–IB — patches and plaques | Scaly, slightly atrophic patches in sun-protected areas; IA covers under 10% of body surface | Good; in stage IA life expectancy is near normal | Potent topical steroids, topical mechlorethamine, NB-UVB or PUVA |
| IIB — tumours | Nodules 1 cm or larger, sometimes ulcerated | Intermediate | Local radiotherapy or total skin electron beam, bexarotene, interferon, mogamulizumab |
| III — erythroderma | Redness over 80% of body surface | Less good | Extracorporeal photopheresis (ECP), systemic therapy |
| Sézary syndrome | Erythroderma, lymph nodes, Sézary cells in blood, intense itch | Poor | ECP, mogamulizumab, brentuximab for CD30-positive cells, stem-cell transplant in selected patients |
| Important mimics | Chronic eczema, psoriasis, large-plaque parapsoriasis, drug reaction | — | Repeated biopsies, immunohistochemistry and T-cell clonality testing |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
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Sources
- EORTC consensus recommendations for mycosis fungoides and Sézary syndrome, 2023 — Staging and treatment
- NCCN Guidelines Primary Cutaneous Lymphomas, 2025 — Mycosis fungoides and Sézary syndrome
- British Association of Dermatologists and UK Cutaneous Lymphoma Group guidelines, 2019 — Primary cutaneous lymphomas
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.