Neurosurgery notes/Tumours/Haematolymphoid and histiocytic tumours/Lymphomas/T-cell and NK/T-cell lymphomas/Peripheral T-cell Lymphoma (PTCL)

Peripheral T-cell Lymphoma (PTCL)

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T-cell and NK/T-cell lymphomas

Definition

  • Essential
    • Biopsy-proven lymphoma manifesting in the CNS.
    • Expression of one or more T-cell markers in variable combination (CD2, CD3, CD4, CD8, CD5, CD7).
  • Desirable
    • Abnormal T-cell immunophenotype with loss of one or more pan-T-cell antigens.
    • Demonstration of clonal TR gene rearrangement, if inflammation is considered in the differential diagnosis.

Numbers

  • Median age in the sixth decade (range 21–81 years)
  • Male preponderance (M:F ratio of about 1.5:1).

Localisation

  • These lymphomas are intra-axial lesions.
  • 29% of patients had multiple brain lesions.
  • Eye involvement was present in 4% of patients
  • 19% had positive cerebrospinal fluid (CSF) cytology.

Clinical Features

  • Headache
  • Neurological decline
  • Seizures
  • Abnormalities of sensory and/or motor function.

Histopathology and Immunophenotype

Macroscopic

  • Necrosis

Microscopic

  • Most cases are categorized as PTCL, NOS (Not Otherwise Specified).
  • They consist of atypical lymphoid cells, typically small to medium-sized, which often exhibit an angiocentric growth pattern and areas of necrosis.
  • The infiltrates include reactive histiocytes and non-neoplastic lymphocytes, while plasma cells, eosinophils, and neutrophils are usually inconspicuous.
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Immunophenotype

  • Neoplastic cells are generally CD3-positive and CD56-negative.
  • They often express cytotoxic granule proteins such as perforin, granzyme B, and/or TIA1.
  • Subsets of cases may show loss of pan-T-cell markers like CD2, CD5, and CD7. The proliferation index is usually high, typically exceeding 50%.

Pathogenesis

  • Molecular Alterations:
    • A subset of cases shows mutations in TET2, DNMT3A, and several genes involved in the JAK/STAT pathway.
    • Clonal rearrangement of the T-cell receptor (TR) genes can be demonstrated in most cases.

Management

  • Methotrexate-based chemotherapy is the typical treatment regimen. In one cohort, the median progression-free survival and overall survival were 22 and 25 months, respectively.

Prognosis

  • The outcome for patients with primary CNS T-cell lymphoma appears similar to that for primary diffuse large B-cell lymphoma of the CNS.
  • Good prognostic factor: Low-grade histological features