OVERVIEW
Non-Hodgkin’s Lymphoma (NHL) is a type of lymphoid typically caused by a clonal proliferation of B-cells or T-cells of the immune system. Abnormal or cancerous B-cell and T-cell lymphocytes can accumulate in the lymph nodes, form solid tumours in the body, or circulate in the blood1.
During maturation of B-cell and T-cell lymphocytes, antigen receptor genes – immunoglobulin (IGH) and T-cell receptor (TCR) – undergo somatic rearrangement in the Variable (V) and Joining (J) regions, and in some cases, the Diversity (D) region. These genetic rearrangements generate products that are unique in both length and sequence, resulting in diverse antigen-binding moieties for adaptive immune response.
There is an estimated 2 million possible rearrangements for the IGH gene and 3 million possible rearrangements for the TCR gene, thus there is negligible chance that two normal lymphocytes bear the same rearrangement2. Malignant lymphocytes are derived from a single neoplastic cell and therefore exhibit identical rearrangements of the IGH or TCR genes. Clonality testing can be used to detect for these clonal rearrangements in suspected lymphoma cases.
INDICATION
B-cell and T-cell clonality testing is offered for patients suspected of Non-Hodgkin’s Lymphoma
TEST REQUIREMENTS
- Completed CGL Lymphoid Testing requisition form
- One of the following specimens (please see our Specimen Guidelines, DNA molecular type)
- 5mL Peripheral Blood in EDTA tube (purple top)
- 1 mL Bone Marrow Aspirate in EDTA tube (purple top)
- Formalin-Fixed Paraffin-Embedded Tissue
Ordering multiple tests? Please review our requirements for multiple samples.
METHOD
Genomic DNA is extracted from the submitted specimen. Rearrangements in the TCR beta gene are detected using multiplex PCR targeting the conserved V, D, and J regions of the TCR beta gene. Rearrangements in the IGH gene are detected using multiplex PCR targeting the conserved V and J regions in frameworks 1, 2, and 3 of the IGH gene.
The resulting PCR products are resolved by capillary electrophoresis and analyzed using associated software. The limit of reliable detection of this assay is 1%, as capillary electrophoresis-based assays cannot reliably detect a clonal population comprising less than 1% of the total lymphocyte cell population.
TURN-AROUND TIME
Results are reported within ten working days from receipt of specimen and completed requisition form.
RESULT REPORTING
Currently 10 – 15% of lymphoid malignancies cannot be accurately distinguished from benign lymphoid proliferations using histopathological findings and immunohistochemical staining alone3,4. Clonality testing is an effective testing method for facilitating the diagnosis of lymphoma.
REFERENCES
- bccancer.bc.ca/health-info/types-of-cancer/blood-lymphoid/non-hodgkin-lymphoma
- van Dongen, J. 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, 2257-2317.
- Gazzola, A. et al. The evolution of clonality testing in the diagnosis and monitoring of hematological malignancies. Ther Adv Hematol. 2014 Apr; 5(2): 35-47.
- Kim, Y. et al. Diagnostic Utility of a Clonality Test for Lymphoproliferative Diseases in Koreans Using the BIOMED-2 PCR Assay. Korean J Pathol. 2013 Oct; 47(5): 458-465.
- Langerak, A. et al. EuroClonality/BIOMED-2 guidelines for interpretation and reporting of Ig/TCR clonality testing in suspected lymphoproliferations. Leukemia (2012) 26, 2159-2171.