Background:
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).
Methodology:
For T-cell receptor beta 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 to identify clonal TRB Vβ—(Dβ—)Jβ region DNA sequences, and provides the frequency distribution of Vβ Dβ and Jβ region segment utilization using the Illumina MisSeq platform. 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.
Specimen Requirements:
Blood/Bone Marrow: EDTA or ACD (Solution A or B):
- Adult: 5-10mL
- Child: 5mL
- Infant: 2-3mL
FFPE: Formalin-fixed paraffin-embedded (FFPE) tissue blocks or 15 unstained slides (5 microns).
Fresh Tissue:
- Stabilize in Allprotect Tissue Reagent (Qiagen) – OR
- Suspend in sterile media (RPMI or DMEM) or non-bacteriostatic normal saline in a sterile container – OR
- Snap Frozen
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)
Pathology report MUST accompany sample for interpretation of results.
A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES. Please include detailed clinical information.
Test Performed (Days):
Once per week
Turn Around Time:
7-10 days
Shipment Sensitivity Requirements:
- Fresh blood, bone marrow, or DNA, package and ship specimen to remain cold, but not frozen.
- Fresh tissue in media, FFPE, or slides, package and ship at room temperature.
- Frozen tissue, package and ship on dry ice. Sample must stay frozen.
- Ship specimens overnight express.
- Contact Client Services for shipping kits and instructions at (855) 535-1522.
References:
- 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.
- 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.
Additional Info: