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T Cell Gene Rearrangement by PCR

Gene Rearrangement, T-cell Gene Rearrangement, T-cell gamma Gene Rearrangement, T-cell Receptor, T-cell PCR, Lymphocyte Gene Rearrangement

Test Codes

EPIC: LAB5128, Beaker: MTCLG

Department

Molecular Pathology

Specimen Collection Criteria

Collect: One of the following specimen types, as described below:

1. Blood: 5.0 mL whole blood in Lavender-top EDTA tubes. Invert several times to mix blood. (Minimum: 3.0 mL)
2. Bone Marrow: 2.0 mL bone marrow in a Lavender-top EDTA tube. Invert several times to mix bone marrow.
3. Spinal Fluid: 10.0 mL spinal fluid in the original sterile collection container. An attempt will be made to extract sufficient DNA from any volume submitted. (Minimum: 5.0 mL)
4. Solid Tissue:
   • Paraffin-Embedded Tissue: A paraffin block must be submitted. (Slides or paraffin shavings are not acceptable.) Submit a 10% formalin-fixed, paraffin-embedded block with corresponding H&E slide. Average tissue size: 5.0 mm². 
   • All specimens types should be sent to the Laboratory immediately for processing.
   • The specimen must be accompanied by a completed requisition and must contain the patient name, hospital and visit number, date of birth, collection date, ordering physician, and source of specimen. 

Physician Office/Draw Specimen Preparation

Maintain whole blood, bone marrow, and spinal fluid at room temperature (20-26°C or 68-78.8°F) or refrigerated (preferred) (2-8°C or 36-46°F) prior to transport. Maintain paraffin-embedded tissue at room temperature (20-26°C or 68-78.8°F).

Preparation for Courier Transport

Transport: Paraffin-embedded tissue at room temperature (20-26°C or 68-78.8°F); blood, bone marrow, or spinal fluid, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

• Anticoagulants other than EDTA or heparin.
• Clotted peripheral blood or bone marrow.
• Fresh or frozen tissue specimen.
• Tissue decalcified in agents other than Mol Decal (EDTA).
• Fixatives other than 10% neutral buffered formalin (e.g., zinc formalin).
• Improper labeling or inadequate information. 
• Less than 10 percent tumor cellularity, at discretion of medical director.
• Poor quality and/or quantity of extracted genomic DNA.

Clients will be notified of any cancellations of testing.

Inpatient Specimen Preparation

Specimens at Royal Oak may be sent to the Surgical Pathology tube station, #201. In-house specimens are also picked up by a Surgical Pathology assistant every hour on the hour.

In-Lab Processing

Maintain whole blood, bone marrow, and spinal fluid refrigerated (2-8°C or 36-46°F), or paraffin-embedded tissue at room temperature (20-26°C or 68-78.8°F) until testing.

Storage

Specimen Stability for Testing:

Blood, Bone Marrow, and Spinal Fluid
Room Temperature (20-26°C or 68-78.8°F): 72 hours
Refrigerated (2-8°C or 36-46°F): 72 hours
Frozen (-20°C/-4°F or below): Unacceptable

Paraffin-Embedded Tissue
Room Temperature (20-26°C or 68-78.8°F): Indefinitely
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Room Temperature (20-26°C or 68-78.8°F): 7 days

Specimen Storage (DNA post testing):

Frozen (-25 to -15°C): 2 months

Laboratory

Royal Oak Molecular Pathology Laboratory

Performed

Monday – Friday.
Results available within 10 business days.

Reference Range

Negative for a monoclonal T-cell receptor rearrangement.

Test Methodology

Following extraction, genomic DNA is amplified via multiplex Polymerase Chain Reaction (PCR) using primers specific for the TCR-gamma gene. Analysis is performed via automated capillary electrophoresis, followed by pathologist interpretation.

Interpretation

An interpretive report will be provided.

Clinical Utility

Detection of a prominent (monoclonal) TCR-gamma gene rearrangement is supportive of a neoplastic T-cell process. However, the results must always be interpreted in the context of other clinicopathologic information as non-neoplastic conditions (e.g., infectious and autoimmune processes) may yield a monoclonal TCR-gamma gene rearrangement.

Limitations:

1. This test is neither 100% sensitive nor 100% specific.
2. False-positive results are not uncommon encountered with polymerase chain reaction (PCR)-based assays. This is usually because the kinetics of end point, competitive PCR are such that the true proportions of rearrangements present may not be maintained during amplification.
3. False-negative PCR results may occur if there is failure of primer binding or if the rearrangement involves a segment that is not bound by the primers used in the assay. False-negative results will also occur if the clonal cells have not rearranged the TCR-gamma genes being evaluated or are present below the sensitivity of the assay (approximately 1-5% of abnormal nucleated cells).
4. This assay cannot determine whether a clonal rearrangement is physiologic or neoplastic.
5. This assay cannot be utilized to definitively assign lineage (i.e., B-cell vs. T-cell) to a neoplastic process.

Reference

1. Vega F, et al. A Novel Four-Color PCR Assay to Assess T-Cell Receptor Gamma Gene Rearrangements in Lymphoproliferative Lesions. Am J Clin Pathol 2001:116:17-24.
2. Coad JE, et al. Molecular Assessment of Clonality in Lymphoproliferative Disorders: II. T-cell Receptor Gene Rearrangements. Mol Diagnosis 1997 Mar;2(1):69-81.

CPT Codes

81342

Contacts

Last Updated

11/2/2023