Mycosis fungoides is an indolent, CD4+ cutaneous T-cell 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 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 cutaneous T-cell lymphoma with leukemic dissemination of mutated T cells can be an advanced form of mycosis fungoides or arise de novo.
- Incidence 
- Age: mostly middle-aged or elderly patients
- Sex: ♂ > ♀
Epidemiological data refers to the US, unless otherwise specified.
- Initially, pruritic cutaneous plaques, patches, and brownish nodules develop. 
- Subsequently, systemic spread occurs, including lymphadenopathy and hepatosplenomegaly.
- Definition: a with leukemic dissemination of mutated T cells
- Exact prevalence unknown
- Can be an advanced form of mycosis fungoides or arise de novo
- Clinical features
- Diagnostics: : based on the characteristic triad of pruritic erythroderma, lymphadenopathy, and atypical T cells (Sézary cells) on peripheral blood smear 
Adult T-cell leukemia (ATL) 
- Definition: a non-Hodgkin lymphoma associated with infection with the HTLV-I) I (
- Rare in the US; most commonly seen in Japan, West Africa, and the Carribean
- Associated with IV drug use
- Clinical features
- 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).
The differential diagnoses listed here are not exhaustive.