Peripheral T cell lymphoma, unspecified (PTCL/U)
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Definition
Peripheral T-cell lymphomas describes a diverse group of blood cancers that originate from T-cells, which may be at various stages of development. These lymphomas usually presents at diagnosis in stage III or IV, and often has an aggressive clinical course requiring prompt treatment. As with all lymphomas the molecular characteristics of the cells, and the stage of development are variable and therefore clinical course can be unique. Peripheral T cell lymphoma, unspecified (PTCL/U), the most common form of PTCL, displays heterogeneous morphology and phenotype, poor response to treatment, and poor prognosis.
Sample Cases
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| Case Name (click on case name to open) |
Comments | Size |
| case 16 | Mature T cell Lymphoma This case was kindly provided by the ASCP Press. It is part of Flow Cytometry in Clinical Diagnosis by John Carey, Phil McCoy and David Keren. |
814 kB |
Epidemiology
More frequent in adults than children. Low incidence - approximately 15-20% of non-Hodgkin's lymphoma. Uncommon in North America. Peripheral T-Cell Lymphoma Unspecified is the most common group. Also see specific variants (subtypes), below. PTCLs/U usually occur in the fifth to sixth decade, with a male-to-female ratio of 1:1 They present as nodal or extranodal disease in 22% and 16% of the cases, respectively, but more often have a widespread dissemination (stage III–IV) with nodal, skin, liver, spleen, bone marrow, and peripheral blood involvement
Possible causes
Morphology
Immunophenotyping
Comparison with the profiles of purified T cell subpopulations (CD4+, CD8+, resting [HLA-DR–], and activated [HLA-DR+]) reveals that PTCLs/U are most closely related to activated peripheral T lymphocytes, either CD4+ or CD8+.
Immunophenotyping generally shows T cell–associated molecule expression, although the phenotypic profile is aberrant in about 80% of cases, with CD5 and CD7 as the most common defective antigens. Nodal cases are more often CD4+, whereas extranodal cases are more often CD8+. In 50% of cases, however, the 2 antigens are either coexpressed (double-positive) or not expressed at all (double-negative)
Other relevant tests
Cytochemistry
Genetics
Products of deregulated genes can be detected in PTCLs/U by immunohistochemistry with an ectopic, paraphysiologic, or stromal location. PTCLs/U aberrantly express, among others, PDGFRα, a tyrosine-kinase receptor, whose deregulation is often related to a malignant phenotype. Notably, both phosphorylation of PDGFRα and sensitivity of cultured PTCL cells to imatinib (as well as to an inhibitor of histone deacetylase) were found. These results, which might be extended to other more rare PTCL categories, provide insight into tumor pathogenesis and clinical management of PTCL/U. Clonal rearrangements of T cell receptor–encoding genes are generally detected. The karyotype is aberrant in more than 80% of cases and often characterized by complex abnormalities. However, specific alterations have not been identified . Recently, some recurrent lesions have been documented by comparative genomic hybridization