• Clinical science

Mycosis fungoides (Cutaneous T-cell lymphoma)


Mycosis fungoides is a chronic, low-grade, malignant, CD4+ T-cell non-Hodgkin lymphoma that presents on the skin. It is characterized by scaly, pruritic, well-demarcated skin plaques and patches that are refractory to initial treatment. In the later stages of the disease, mushroom-shaped tumors develop within the plaque lesions, and ultimately lymphadenopathy and hepatosplenomegaly can develop. Mycosis fungoides, which is based on the fungus-like growth pattern of the lesions, is misleading as the disease is not fungal in origin. Histopathological evidence is essential for diagnosis and typically consists of atypical lymphocytes found in the upper dermis or aggregates of such cells within the epidermis (known as Pautrier's microabscesses). Early treatment consists of topical glucocorticoids, while treatment for later stages involves a combination of localized radiation, electron beam therapy, and systemic chemotherapy. Sézary syndrome, a T-cell leukemia, is considered an advanced stage of mycosis fungoides.


  • Uncommon: only 4% of non-Hodgkin lymphoma cases
  • Age: mostly middle-aged or elderly patients
  • Mycosis fungoides and Sézary syndrome are the two most common cutaneous T-cell lymphomas.


Epidemiological data refers to the US, unless otherwise specified.

Clinical features




Differential diagnoses

Sézary syndrome

  • Cutaneous T-cell lymphoma with leukemic dissemination of mutated T cells
  • Can be an advanced form of mycosis fungoides or arise de novo
  • Characteristic triad of symptoms
  • The leukemic dissemination present in Sézary syndrome distinguishes it from mycosis fungoides.


  • Initial lesions of mycosis fungoides can be confused with eczema due to the erythematous and pruritic patches or plaques.
  • Mycosis fungoides is less likely to respond to initial treatment for eczema (including topical glucocorticoids).

Adult T-cell leukemia (ATL)

  • Definition: A non-Hodgkin lymphoma associated with infection with the human lymphotropic virus I (HTLV-I)
  • Epidemiology
    • ATL is rare in the US; most commonly seen in Japan, West Africa, and the Carribean.
    • Associated with IV drug use.
  • Clinical features
    • Generalized lymphadenopathy
    • Hepatosplenomegaly
    • Skin lesions: The lesions seen in mycosis fungoides may be similar to those seen in ATL.
    • Hypercalcemia
    • Lytic bone lesion
  • Diagnostics
    • Peripheral blood smear: lymphocytes with condensed chromatin and hyperlobulated nuclei that resemble clover leaves
    • Immunophenotype: stain positive for CD3, CD4, CD7, CD8, and CD25


The differential diagnoses listed here are not exhaustive.


  • Treatment for early stage disease:
    • Topical corticosteroids (first-line)
    • Topical nitrogen mustard (second-line)
  • Treatment for moderate to late stage disease: