What is the Difference Between Mycosis Fungoides and Sezary Syndrome?

Mycosis fungoides and Sézary syndrome are both cutaneous T-cell lymphomas (CTCLs), but they have distinct differences in their clinical presentation, diagnosis, and prognosis.

Mycosis Fungoides:

Affects the skin in the form of patches, plaques, and tumors.
Diagnosis is based on the presence of specific types of malignant T cells in the skin biopsy.
Staging involves the primary tumor (T), lymph node involvement (N), organ metastases (M), and the number of tumor cells in the peripheral blood (B).
It is the most common primary cutaneous lymphoma.

Sézary Syndrome:

Affects both the skin and the blood, with visible skin lesions and large numbers of Sézary cells in the blood.
Diagnosis requires the presence of a specific level of Sézary cells in the blood, as well as a positive clone or CD4/CD8 ratio of 10 or more.
Patients typically present with diffuse erythema and leukemic disease.

It is still unclear whether Sézary syndrome is an advanced form of mycosis fungoides or a separate disease. The two conditions arise from distinct T-cell subsets, with Sézary syndrome being a malignancy of central memory T cells and mycosis fungoides being a malignancy of skin-resident effector memory T cells. Prognosis and treatment options for both conditions depend on various factors, including the stage of the disease and the presence of specific evidence in the skin and blood.

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What is the Difference Between Mycosis Fungoides and Sezary Syndrome?

Comparative Table: Mycosis Fungoides vs Sezary Syndrome

Mycosis fungoides (MF) and Sézary syndrome (SS) are the most common malignancies among cutaneous T-cell lymphomas (CTCLs). Here is a table summarizing the differences between the two:

Feature	Mycosis Fungoides	Sézary Syndrome
Etiology	Not fully understood	Not fully understood
Pathogenesis	Not yet fully understood	Not yet fully understood
Clinical Stages	Presents with various clinical stages	Diagnosed based on at least one of the following criteria: absolute Sézary cell count > 1000/μL, CD4+/CD8+ ratio ≥ 10, CD4+/CD7– cells ≥ 40%, or CD4+/CD26– cells ≥ 30%
Staging	Performed according to the TNMB classification (T: primary tumor, N: lymph node involvement, M: organ metastases, B: number of tumor cells in the peripheral blood)	Peripheral blood involvement is an essential diagnostic component
Cell Type	Originates from different T-cell types	Sézary cells arise from "central memory T cells"
Diagnosis	Difficult in early stages, relies on clinicopathological correlation	Diagnosis and staging based on peripheral blood findings
Prognosis	Factors that aggravate prognosis include clinical stage and medical history	Prognosis is influenced by the clinical stage and peripheral blood involvement

It is essential to evaluate peripheral blood involvement and the medical history in order to determine the appropriate treatment plan for both mycosis fungoides and Sézary syndrome.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.