Your pathology report for Sezary syndrome

by Jason Wasserman MD PhD FRCPC and David Li MD
May 29, 2025

Sézary syndrome is a rare type of cancer involving specific white blood cells called T cells. Normally, T cells help fight infections and diseases. In Sézary syndrome, these cells become cancerous and multiply out of control. The cancerous T cells, known as Sézary cells, exhibit a unique, folded appearance under the microscope. These abnormal cells accumulate in the skin, causing widespread redness and irritation (erythroderma), in the lymph nodes, resulting in swelling, and the bloodstream.

What are the symptoms of Sézary syndrome?

The most common symptoms of Sézary syndrome include:

  • Widespread redness and scaling of the skin (erythroderma).
  • Severe itching (pruritus).
  • Enlarged lymph nodes (generalized lymphadenopathy).
  • Hair loss (alopecia).
  • Thickening of the skin on palms and soles (hyperkeratosis).
  • Thick, leathery skin changes (lichenification).
  • Abnormal nail growth (onychodystrophy).
  • Outward turning of the eyelids (ectropion).

Some patients might also experience an increased risk of developing other cancers due to weakened immunity.

What causes Sézary syndrome?

The exact cause of Sézary syndrome is unknown. However, recent studies suggest that exposure to ultraviolet (UV) radiation plays a significant role in this process. UV radiation is thought to damage T cells in the skin, leading to mutations that transform normal T cells into cancerous Sézary cells. Genetic changes affecting various pathways involved in immune system regulation and DNA repair also contribute to disease development.

Who gets Sézary syndrome?

Sézary syndrome is a very rare condition, affecting a small number of adults. It typically occurs in people older than 60 and is more common in men than in women. Sézary syndrome accounts for a small percentage (approximately 2-3%) of all skin-related T cell cancers.

What parts of the body are typically affected by this disease?

Sézary syndrome primarily affects the skin, causing widespread redness (erythroderma). It often involves lymph nodes, causing them to swell. In more advanced stages, it can spread to internal organs, such as the lungs, mouth, and throat (oropharynx), as well as the central nervous system.

How is this diagnosis made?

To diagnose Sézary syndrome, your doctor will typically evaluate blood samples, skin biopsies, and lymph node biopsies. A pathologist examines these samples under the microscope, looking for Sézary cells, which have distinctive folded nuclei. These cells must be identified in blood and tissue samples from the skin or lymph nodes to confirm the diagnosis. Bone marrow biopsies may occasionally be used to identify Sézary cells, although their presence is usually sparse in this tissue.

What additional tests may be performed to confirm the diagnosis?

Several specialized tests can confirm Sézary syndrome:

  • Immunohistochemistry (IHC): This test uses antibodies to identify specific proteins on the surface of Sézary cells. Typical findings include positive staining for proteins such as CD3, CD4, PD-1, CCR4, and CCR7. There is often a loss of other markers, such as CD7 or CD26.
  • Flow cytometry: Flow cytometry analyzes cells from blood or tissue samples to identify unique protein patterns. In Sézary syndrome, this typically presents with an increased number of CD4+ T cells exhibiting abnormal protein expression, such as the absence of CD7 or CD26.
  • Molecular tests for T cell clonality: Special genetic tests may be done to see if the T-cells are clonal. “Clonal” means that all cancerous cells originated from the same abnormal parent cell. These tests help confirm that the disease is cancerous and not a benign condition.

What is the prognosis for someone diagnosed with Sézary syndrome?

Sézary syndrome is an aggressive disease, and its prognosis varies based on the stage at diagnosis. The median survival is approximately 32 months, with 5-year survival rates ranging from 10% to 30%. Patients often succumb to infections due to weakened immunity. Early detection and ongoing management by specialists can improve outcomes and help control symptoms.

Questions to ask your doctor

  • What stage is my Sézary syndrome?
  • What treatment options are available, and which do you recommend?
  • What are the potential side effects of treatment?
  • How often will I need follow-up tests or check-ups?
  • What symptoms should prompt me to contact you immediately?
  • Are there clinical trials or newer treatments available that might benefit me?
  • Can lifestyle changes help manage my symptoms or improve my overall health?
A+ A A-