Heterogeneous group of uncommon disorders characterised by clonal accumulation of T lymphocytes primarily or exclusively in the skin. Mycosis fungoides and its leukaemic variant, Sézary's syndrome, are the most common subtypes.
Establishing a diagnosis is often difficult, as the disease can take many different forms in the skin: flat patches, raised plaques, large tumours, and/or marked erythroderma (intense and widespread reddening of the skin).
Diagnosis is based on clinical findings, skin biopsy, and laboratory blood tests, and usually requires specialist expertise.
Early-stage disease is usually managed with skin-directed therapy (topical medications, phototherapy, and localised radiotherapy). If skin disease progresses, or the patient presents with advanced disease, systemic therapies are often necessary (chemotherapy, biological or immunological therapy, photopheresis).
Clinical trials may be considered in early and advanced disease. The choice of skin-directed therapy or systemic treatment is usually dependent on both doctor and patient preference, as no one treatment option has been shown to be superior to another.
Prognosis is closely related to the stage at diagnosis. Survival rates in early disease are excellent. However, although treatment may induce remission, patients are expected to relapse after a variable interval and are unlikely to be cured.
Cutaneous T-cell lymphomas (CTCL) make up a heterogeneous group of uncommon disorders characterised by clonal accumulation of T lymphocytes primarily or exclusively in the skin. Mycosis fungoides (MF) and its leukaemic variant, Sézary's syndrome (SS), are the most common subtypes.  MF frequently behaves as an indolent lymphoma with good prognosis for early-stage disease, while SS is considered a more aggressive form of the disease, associated with shortened survival.
Professor of Targeted Therapy and Oncology
University of Manchester
Manchester Academic Health Sciences Centre
TMI declares that he has no competing interests.
Consultant in Clinical Oncology
Christie NHS Foundation Trust
RC declares that he has no competing interests.
Tameside Hospital Integrated Care Organisation NHS Trust
EP declares she has no competing interests.
Department of Radiation Oncology
Duke University School of Medicine
CK declares that he has no competing interests.
Professor and Head of Dermatology
Department of Medicine
New Jersey Medical School
RAS declares that he has no competing interests.
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