Hematological Malignancies T-Cell Receptor (TCR) Gamma Gene Rearrangement

T-cell lymphomas account for approximately 15% of non-Hodgkin lymphomas and may pose a diagnostic challenge on the basis of histopathology alone and particularly in early stages of disease. The heterodimeric T-cell surface receptors, either alpha/beta (90% -95% of T cells) or gamma/delta (5% - 10% of T cells) are produced following somatic rearrangement of the T-cell receptor (TCR) genes (alpha, beta, delta, and gamma). This process is vital to proliferation of T-cells in normal immune function, but can be exploited to aid in the distinction between reactive (benign) versus neoplastic processes of T-cell proliferation. A reactive, benign T-cell proliferation is characterized by polyclonal expansion of T-cells whereas a malignant process is characterized by clonal expansion of one T-cell population. In conjunction with morphologic evaluation of lymph nodes, bone marrow and other tissue types the detection of a clonal T-cell gene rearrangement by polymerase chain reaction (PCR) can be used to aid a diagnosis of malignant T-cell lymphoma.

Clinical Utility:
PCR-based detection of rearranged T-cell receptor genes can be used to help establish a diagnosis of T-cell lymphoma, monitor for treatment response, and/or measure minimal residual disease (MRD). 

For T-cell receptor gamma targets, extracted genomic DNA from blood, lymph node, bone marrow, or other tissue types are PCR amplified and subjected to next generation sequencing (NGS) library preparation with a combination of heterogeneous TCR-gamma V(variable) region and J-(joining) region primers to generate TCR-gamma receptor VJ-rearranged templates, which are then subjected to next-generation sequencing on a MiSeq instrument. The number and frequency of NGS sequencing reads from these rearranged VJ segment are then analyzed to assess the possible presence of a predominating clonal T-cell population. The analytical sensitivity limit for detecting low level T-cell clones with this NGS based method is approximately 6%. Clonal lymphocyte populations below this sensitivity threshold will not be detected. In addition, due to the great diversity of immune cell antigen receptor recombination breakpoints, only ~85% of all clonal T-cell populations will be identified with the primers utilized in this assay.

Clinical Sensitivity:
Approximately 85%

Clinical Specificity:
As cross-lineage TCR gene rearrangements have been reported in immature B-cell malignancies, interpretation of this test requires clinical, morphologic, and immunophenotypic correlation.

• 5-10 mL of blood or bone marrow — yellow (ACD) or purple (EDTA) tube. Store and ship refrigerated. 
• Formalin-fixed paraffin-embedded (FFPE) tissue blocks or minimum 15 slides (5 microns). Store and ship at room temperature.
• Pathology report MUST accompany sample for interpretation of results.

DNA: 200g at a minimum of 10ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS)

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES.  Please include detailed clinical information.

Once per week

7-10 days

• Keep specimen cold during transit, but do not ship on dry ice.
• Please use the cold pack provided in the KDL shipping kit.
• Ship the specimen overnight express, using the FedEx priority overnight label provided.

1. Van Dongen JJ, Langerak AW, Bruggemann M, et al. Design and standardization of PCR primers and protocols for detection of clonal immunoglobulin and T-cell receptor gene recombinations in suspect lymphoproliferations: report of the BIOMED-2 Concerted Action BMH4-CT98-3936. Leukemia 2003; 17(12):2257-2317.
2. Langerak AW, Molina TJ, Lavender FL, et al. Polymerase chain reaction-based clonality testing in tissue samples with reactive lymphoproliferations: usefulness and pitfalls. Report of the BIOMED-2 Concerted Action BMH4-CT98-3936. Leukemia 2007; 21:222-229.