Mycosis fungoides & cutaneous T-cell lymphoma
Also called CTCL, cutaneous T-cell lymphoma, MF
A T-cell lymphoma that lives in skin and impersonates eczema and psoriasis for years: fixed, oddly shaped patches in sun-protected skin that partially respond to steroids and always come back. The lesson for the non-specialist is one sentence: biopsy the chronic dermatitis that never behaves.
How it looks
Fixed, asymmetric, sharply and irregularly bordered erythematous patches with fine wrinkling and scale over sun-protected buttock and trunk skin.
Rose is the lesion, grey the pattern the lesions make, green where on the body it lives.
Across skin tones
Hypopigmented MF is the characteristic presentation in deeply pigmented and younger patients, where classic erythema is also harder to see; persistent pale patches with subtle scale or atrophy in sun-protected sites deserve biopsy, not a versicolor label by default.
Don't miss
Erythroderma with lymphadenopathy and unbearable itch is Sezary syndrome until the blood says otherwise; it is the erythroderma cause most often missed for years.
Forms & variants
Patch, plaque, and tumour stages
The classic march over years: wrinkled erythematous patches in sun-protected 'bathing-trunk' skin, then infiltrated plaques, then ulcerating tumours.
Hypopigmented MF
Pale patches in young, deeply pigmented patients, the great vitiligo and versicolor mimic; biopsy pale patches that scale, itch, or persist oddly.
Folliculotropic MF
Follicle-centred plaques with alopecia and comedone-like lesions, often head and neck; behaves more aggressively than classic patches.
Bullous MF and pagetoid reticulosis
Rare forms: blistering disease, or a solitary slowly expanding acral keratotic plaque (Woringer-Kolopp) with indolent behaviour.
Granulomatous slack skin syndrome
Exceptionally rare: pendulous lax skin folds in flexural areas from granulomatous destruction of elastic fibres.
Sezary syndrome
The leukaemic red flag: erythroderma, lymphadenopathy, and circulating atypical (Sezary) cells, with relentless itch; aggressive disease needing systemic therapy.
Parapsoriasis
Chronic asymptomatic scaly patches that may precede MF; small-plaque disease is mostly benign, large-plaque disease is the one surveilled with biopsies.
Lymphomatoid papulosis
Crops of self-healing papulonodules that look alarming and biopsy like lymphoma yet follow a benign relapsing course; it earns long-term follow-up for associated lymphomas.
Symptoms & course
- Itch, from mild to intractable
- Lesions fixed in place for months to years
- Partial steroid response with prompt relapse
Diagnostic approach
- Multiple biopsies from untreated lesions (stop topical steroids 2-4 weeks first)
- Histology, immunophenotype, and T-cell clonality together
- Staging: examination of nodes, blood film and flow for Sezary cells when erythrodermic
Differential, and how to separate them
- Psoriasis
Favours it: Chronic well-demarcated scaly plaques
Against it: Psoriasis is symmetric and extensor with micaceous scale; MF is asymmetric, wrinkled, and sun-protected
- Atopic dermatitis
Favours it: Chronic itchy 'eczema' on trunk and limbs
Against it: Atopic disease flexes, flares, and moves; MF patches hold their exact ground for years
- Tinea corporis
Favours it: Annular scaly patches
Against it: KOH negative, and no antifungal touches it; a 'ringworm' that survived two courses is a biopsy
Management principles
- Skin-directed therapy for early disease: potent topical steroids, phototherapy, radiotherapy for localized plaques
- Systemic therapy for advanced or Sezary disease, in specialist hands
- The itch is a treatment target in its own right
Clinical pearl: The referral letter that says 'eczema, fifteen years, never fully clears, always the same places' describes mycosis fungoides more often than eczema.
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