Heterogeneous group of lesions with variable clinical and histopathological manifestations.
Comprised 10-15% of all lymphomas.
PTCLs account for 6% to 10% of all cases of NHL, making them exceedingly rare
Majority of T cell lymphomas are aggressive in nature.
Patients with peripheral T-cell lymphomas (PTCL) have a particularly poor prognosis due to aggressive course and lack of effective treatments.
T Cells are born in the bone marrow, and undergo T cell receptor (TCR) gene rearrangements in the thymus and eventually emerge as mature T lymphocytes.
The diversity of PTCL is attributed to the wide spectrum of activity of T cells, which can be divided into many sub types of cells including: T-helper (TH), natural killer (NK) cells, suppressor T cells, cytotoxic T cells, memory T cells, regulatory T cells (Tregs) and gamma delta T cells.
The most aggressive T-cell lymphoma subtypes are PTCL (peripheral T-cell lymphoma) occurring in 25.9% of cases and the next most common type is angioimmunoblastic T-cell lymphoma (AITL) 18.5%, NK/T-cell lymphoma 10.4%, adult T-cell lymphoma/leukemia (ATLL) 9.6% and anaplastic large cell lymphoma (ALCL)-ALK+ 6.6%, and ALK-5.5%(The International T-Cell Lymphoma Project).
Accounts for approximately 15% of non-Hodgkin’s lymphomas.
Marked geographic variation among the subtypes with PTCL-NOS the most frequent subtype in North America and Europe, but occurs less often in the Far East.
NK/T-cell lymphoma and ATLL occur with greater frequency in the Far East then North America or Europe.
ALK-positive ALCL more than twice as frequent in North America then and Europe and AITL rates are highest in Europe.
Approximately 5000 new cases annually in the U.S.
Chemotherapy responses limited compared to aggressive B cell lymphomas with most patients relapsing after initial treatment.
Often has a worse prognosis than B cell lymphoma.
The most common T-cell marker is CD3, a pan T.-cell marker because it is generally present in all types of T cells.
Other subset T cell markers are CD2, CD5 and CD7 which are expressed by nonmalignant T cells.
Normal T cells express CD3, CD2, CD5, and CD7.
The most common genomic abnormality in T-cell lymphomas is the loss of some T cell markers most commonly CD7, followed by CD5 and in CD2.
Response rate to CHOP chemotherapy in T cell lymphoma results in 3-year overall survival of 62% compared to 56% for patients treated with more intensive regimens.