Sézary cells


A type of T-cell lymphoma mainly occurring after 60 years of age. Cells have characteristic morphology. Skin involvement is usual, and histology from involved areas will generally allow diagnosis. Sézary cells may be detected in the context of mycosis fungoides, or may be found in de novo cases. Erythroderma, lymph node, liver and spleen involvement are the most typical clinical findings



  • The number of neoplastic Sézary cells should be greater than 1 x109/L in blood.
  • Morphology is typically quite variable, and cells may be small, large or have mixed appearance
  • Typically, the nucleocytoplasmic ratio is high, cytoplasm is moderately basophilic; small vacuoles may sometimes be present
  • Dense irregular or folded nuclear lobes (more obvious in larger cells), small cell variants may resemble normal lymphocytes
  • A complex folded “cerebriform” nuclear appearance is considered typical when present

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Sézary syndrome

Sézary cells. The film shows the typical medium-sized abnormal cells with tight nuclear convolution that is typical of Sézary cells as well as the expected variability in size and shape. The nuclear convolution is typically difficult to see unless looked for - this is particularly true of photographed cells but also down the microscope. At least one cell shows the typical small vacuoles around the nucleus that are frequently seen in the disorder.

AUDIO COMMENTARY: Diagnosis of Sézary syndrome



Flow cytometry is an essential part of the diagnosis of the Sézary syndrome. Sézary cells typically have the immunophenotype of mature T cells that express CD4 with α/β TCR type, so an expanded population of CD4 cells (recorded as absolute number) is expected. In almost all cases there are additional aberrant features such an absence of CD26 and CD7,

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(1) T cell gene rearrangement: Will confirm T cell clonality and is therefore an essential element of diagnosis

(2) Cytogenetics: Lesions are often present, the most frequent include monosomy 10, loss of 10q and 17p, gains of 8q24 and 17q, as well as indication of chromosomal instability.

(3) Dysregulated gene expression: It is recognised that many genes have a dysregulated pattern expression, but is no diagnostic pattern or single causative gene has yet emerged.

(4) Clinical and histopathological characterisation is fundamental to diagnosis