Mycosis Fungoides & Sézary Syndrome

What is mycosis fungoides (MF)?

A cutaneous T-cell lymphoma characterized by malignant T cells infiltrating the skin.

What type of lymphoma is MF?

Indolent non-Hodgkin T-cell lymphoma.

What is the cell of origin in MF?

CD4+ helper T cells.

Where does MF primarily manifest?

Skin.

What is the typical age group for MF?

Middle-aged to older adults.

What is the earliest stage of MF?

Patch stage with flat, scaly lesions resembling eczema.

What characterizes the plaque stage of MF?

Thickened, raised skin lesions.

What defines the tumor stage of MF?

Nodular lesions that may ulcerate.

What is a hallmark histologic feature of MF?

Epidermotropism (T cells infiltrating epidermis).

What are Pautrier microabscesses?

Collections of malignant T cells within the epidermis.

What is the typical immunophenotype of MF?

CD3+, CD4+, CD45RO+ T cells.

What symptoms are common in MF?

Pruritus (itching) and chronic skin lesions.

Why is MF often misdiagnosed early?

It resembles benign skin conditions like eczema or psoriasis.

What is Sézary syndrome?

A leukemic variant of cutaneous T-cell lymphoma with systemic involvement.

What triad defines Sézary syndrome?

Erythroderma, lymphadenopathy, and circulating malignant T cells.

What is erythroderma?

Diffuse redness and scaling of the skin over most of the body.

What are Sézary cells?

Malignant T cells with cerebriform (brain-like) nuclei in blood.

What causes the cerebriform nucleus appearance?

Folded nuclear membrane of malignant T cells.

What distinguishes Sézary syndrome from MF?

Peripheral blood involvement and systemic disease.

What is the prognosis of Sézary syndrome?

Worse than MF due to systemic spread.

What is the progression pattern of MF?

Slow progression from patches → plaques → tumors.

What is lymphadenopathy in MF?

Enlargement of lymph nodes due to spread of malignant cells.

What is the role of biopsy in MF diagnosis?

Confirms diagnosis by identifying malignant T cells in skin.

What is clonality testing in MF?

Detects identical T-cell receptor gene rearrangements.

What does T-cell clonality indicate?

Malignant proliferation of a single T-cell clone.

What is the role of flow cytometry in Sézary syndrome?

Detects abnormal T cells in blood.

What are common lab findings in Sézary syndrome?

Elevated Sézary cell count and abnormal CD4:CD8 ratio.

What is the CD4:CD8 ratio in Sézary syndrome?

Elevated due to expansion of CD4+ malignant cells.

What is the pathophysiology of MF?

Malignant T cells home to skin and evade immune regulation.

Why do MF cells localize to skin?

Expression of skin-homing receptors such as CLA.

What is CLA?

Cutaneous lymphocyte antigen directing T cells to skin.

What are common complications of MF?

Infections due to impaired skin barrier and immune dysfunction.

Why are infections common in advanced MF?

Loss of skin integrity and immune suppression.

What is the first-line treatment for early MF?

Topical corticosteroids and phototherapy.

What type of phototherapy is used in MF?

PUVA (psoralen + UVA).

What is the role of radiation therapy in MF?

Used for localized tumors or resistant lesions.

What systemic therapies are used in advanced MF?

Retinoids, interferon, chemotherapy, and biologics.

What is the role of extracorporeal photopheresis?

Treatment for Sézary syndrome involving leukocyte modification.

How does photopheresis work?

Blood is treated with light-activated agents to kill malignant T cells.

What is the goal of MF treatment?

Control symptoms and slow progression.

Is MF curable?

Usually not, but manageable in early stages.

What is the key difference between MF and B-cell lymphomas?

MF is T-cell derived and primarily affects skin.

What is the hallmark clinical feature of MF?

Chronic, pruritic skin lesions that progress over time.

What is the hallmark feature of Sézary syndrome?

Circulating malignant T cells with erythroderma.

What is the major prognostic factor in MF?

Stage of disease at diagnosis.

What is the risk of transformation in MF?

May progress to more aggressive lymphoma.

What is the key clinical takeaway of MF and Sézary syndrome?

Cutaneous T-cell lymphomas with skin manifestations and potential systemic spread.