TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: TLBLF    
T-Lymphoblastic Leukemia/Lymphoma, FISH, Tissue

Useful For Suggests clinical disorders or settings where the test may be helpful

Detecting a neoplastic clone associated with the common chromosome abnormalities seen in patients with T-cell lymphoblastic leukemia or lymphoma

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

This test may be ordered in 2 distinct ways allowing different combinations of probes to be utilized based on the clinical question, including the standard (diagnostic) TLBL FISH panel and the individual TLBL FISH probes (per client request).

 

The specific TLBL FISH panel or probes requested must be noted on the request form or in the reason for referral. If no specific panel or FISH probes are indicated, the standard (diagnostic) panel will be performed.

 

The standard (diagnostic) panel includes testing for the following abnormalities, using the FISH probes listed:

-1p33 rearrangements, TAL1/STIL(SIL)

-t(5;14)(q35;q32), TLX3(HOX11L2)/BCL11B

-7q34 rearrangements, TRB(TCR beta)

-9p-, CDKN2A(p16)/D9Z1

-t(9;22)(q34;q11.2), ABL1 amplification, ABL1(ABL)/BCR

-t(10;11)(p12;q14), MLLT10(AF10)/PICALM

-11q23 rearrangements, MLL

-14q11.2 rearrangements, TRAD (TCR alpha delta)

-17p-, TP53/D17Z1

 

When an MLL rearrangement is identified, reflex testing will be performed with 1 or more dual-fusion probe sets (D-FISH) in an attempt to identify the translocation partner. Probes include:

-t(4;11)(q21;q23), AFF1(AF4)/MLL

-t(6;11)(q27;q23), MLLT4(AF6)/MLL

-t(9;11)(p22;q23), MLLT3(AF9)/MLL

-t(10;11)(p12;q23), MLLT10(AF10)/MLL

-t(11;19)(q23;p13.1), MLL/ELL

-t(11;19)(q23;p13.3), MLL/MLLT1(ENL)

 

When an TRB(TCR beta) rearrangement is identified, reflex testing will be performed with a dual-fusion probe sets

(D-FISH) in an attempt to identify the translocation partner.

-t(7;10)(q34;q24), TRB(TCR beta)/TLX1(HOX11)

 

When an TRAD(TCR alpha delta) rearrangement is identified, reflex testing will be performed with a dual-fusion probe sets

(D-FISH) in an attempt to identify the translocation partner.

-t(10;14)(q24;q11.2), TLX1(HOX11)/TRAD(TCR alpha delta)

 

This test includes a charge for application of the first probe set (2 FISH probes) and professional interpretation of results. Additional charges will be incurred for all reflex probes performed. Analysis charges will be incurred based on the number of cells analyzed per probe set. If no cells are available for analysis, no analysis charges will be incurred.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

T-lymphoblastic lymphoma (T-LBL) is the non-leukemic form of T-acute lymphoblastic leukemia (T-ALL). In the United States, the incidence of ALL is roughly 6,000 new cases per year (as of 2009), or approximately 1 in 50,000. ALL accounts for approximately 70 percent of all childhood leukemia cases (ages 0 to 19 years), making it the most common type of childhood cancer. Approximately 85% of pediatric ALL cases are B-cell lineage (B-ALL) and 15% are T-cell lineage (T-ALL). T-ALL is more common in adolescents than younger children and accounts for 25% of adult ALL. When occurring as a primary lymphoblastic lymphoma, approximately 90% are T-cell lineage versus only 10% B-cell lineage. T-LBL characteristically presents in adolescents and young adults as a mediastinal mass with or without concurrent bone marrow involvement. It is not uncommon that the only sample available with T-LBL involvement is a paraffin-embedded mediastinal or lymph node biopsy specimen.

 

Specific genetic abnormalities can be identified in the majority of T-ALL/LBL cases, although many of the classic abnormalities are “cryptic” by conventional chromosome studies and must be identified by fluorescence in situ hybridization (FISH) studies. Each of the genetic subgroups are important to detect and can be critical prognostic markers. One predictive marker, amplification of the ABL1 gene region, has been identified in 5% of T-ALL, and these patients may be responsive to targeted tyrosine kinase inhibitors. A combination of cytogenetic and FISH testing is currently recommended in all pediatric and adult patients to characterize the T-ALL/LBL clone for prognostic genetic subgroups.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

A positive result is detected when the percent of cells with an abnormality exceeds the normal cutoff for the probe set.

 

A positive result is not diagnostic for T-lymphoblastic lymphoma (T-LBL), but may provide relevant prognostic information.

 

The absence of an abnormal clone does not rule out the presence of neoplastic disorder.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is not approved by the US Food and Drug Administration, and it is best used as an adjunct to existing clinical and pathologic information.

 

Fixatives other than formalin (eg, Prefer, Bouin) may not be successful for FISH assays. Although FISH testing will not be rejected due to nonformalin fixation, results may be compromised.

 

Paraffin-embedded tissues that have been decalcified are generally unsuccessful for FISH analysis. The pathologist reviewing the hematoxylin and eosin-stained slide may find it necessary to cancel testing.

Supportive Data

For each probe set, blinded FISH analysis was performed on 25 normal paraffin-embedded, formalin-fixed tissue controls and 32 to 36 paraffin-embedded, formalin-fixed tissue samples from patients diagnosed with T-cell lymphoblastic leukemia or lymphoma. Results from the 25 controls were used to generate the normal cutoff values.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Graux C, Cools J, Michaux L, et al: Cytogenetics and molecular genetics of T-cell acute lymphoblastic leukemia: from thymocyte to lymphoblast. Leukemia 2006;20:1496-1510

2. Swerdlow SH, Campo E, Stefano PA, et al: The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood 2016;127(20):2375-2390

3. van Grotel M, Meijerink JP, Beverloo HB, et al: The outcome of molecular-cytogenetic subgroups in pediatric T-cell acute lymphoblastic leukemia: a retrospective study of patients treated according to DCOG or COALL protocols. Haematologica 2006;91:1212-1221

4. World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues. Edited by SH Swerdlow, E Campo, NL Harris, et al. Lyon, IARC Press, 2017