Mycosis fungoides — cutaneous T-cell lymphoma — treatment notes

24Mycosis fungoides — cutaneous T-cell lymphoma

Snapshot. The commonest cutaneous T-cell lymphoma (CTCL) — an indolent clone of CD4+ T cells RESIDENT IN SKIN. Not a fungus, and not a keratinocyte "skin cancer": the skin is the address, not the culprit. Masquerades for years as eczema/psoriasis that never quite responds — diagnosis is biopsy (epidermotropic atypical T cells, Pautrier microabscesses) + clonality. Staging IS the natural history: patches/plaques (IA–IIA) → tumours (IIB) → erythroderma (III) → nodes/blood/viscera (IV); the leukaemic phase (erythroderma + circulating clone) = Sézary syndrome. Most early-stage patients never progress.

Workup

Skin biopsy + immunophenotype + T-cell clonality (often needs repeat biopsies over time) · full skin map with %BSA + T-stage · node exam every visit → excise/biopsy if significant · erythroderma → FLOW CYTOMETRY for Sézary cells (CD4:CD8 ratio, Sézary count) · LDH · imaging only for advanced stage or symptoms · CD30 status on biopsy (opens brentuximab) · watch for large-cell transformation (a nodule that suddenly grows → re-biopsy).

Treatment by setting

Setting	Treatment
EARLY — patch / plaque (IA–IIA)	SKIN-DIRECTED ONLY — systemic therapy is deliberately withheld it adds toxicity without survival benefit at this stage · stage IA = essentially NORMAL life expectancy (most die with it, not of it); IB–IIA = long survival, commonly a decade or two, many never progress — counsel: a condition you live with, watched, for decades Phototherapy — narrowband UVB (patches/thin plaques) · PUVA (psoralen + ultraviolet A; thicker plaques) UV kills the lymphocytes sitting in the epidermis · ⚠ cumulative PUVA carries its own skin-cancer risk → whole-skin surveillance Potent topical steroids · topical mechlorethamine gel · local radiotherapy for a solitary stubborn lesion MF is exquisitely radiosensitive · itch control (emollients ± antihistamine/gabapentinoid) — itch severity tracks disease
REFRACTORY early / advancing	Gentle systemics: BEXAROTENE (oral retinoid) · interferon · low-dose methotrexate · HDAC (histone-deacetylase) inhibitors (vorinostat, romidepsin) ⚠ bexarotene's signature pair: HYPERTRIGLYCERIDAEMIA + CENTRAL HYPOTHYROIDISM (low TSH AND low T4 — check lipids + TFTs) Total-skin electron-beam therapy (TSEBT) when the whole surface needs clearing · tumour-stage (IIB) disease steps the outlook down — median ~4–5 yr (historical series; varies between cohorts)
ADVANCED / blood / transformed	CD30-positive → BRENTUXIMAB VEDOTIN (ALCANZA) anti-CD30 antibody-drug conjugate — watch neuropathy Blood involvement / Sézary → MOGAMULIZUMAB (MAVORIC) · extracorporeal photopheresis anti-CCR4 antibody — watch rash (can mimic the disease); photopheresis suits erythrodermic disease Cytotoxic chemo LATE (gemcitabine, liposomal doxorubicin) — responses real but SHORT chemo does not control CTCL durably — hence the biologic-first ladder Young + aggressive → allogeneic stem-cell transplant — the only potentially curative move erythrodermic (III) ~3–5 yr · IV / Sézary median ~2–4 yr — historical-series figures, the reason transplant is on the table for the young

Watch

Progression signals: a nodule that grows (transformation → re-biopsy) · new nodes · erythroderma (→ flow cytometry). PUVA → cumulative squamous skin cancers. Bexarotene → triglycerides + central hypothyroidism. Romidepsin → QT prolongation, cytopenias. Mogamulizumab → rash (biopsy to separate drug from disease) — and reported worse GvHD if transplant follows soon after. Relentless itch → treat it; it is the disease speaking.