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Test ID: FRTAL    
T-Cell Acute Lymphoblastic Leukemia (T-ALL), FISH

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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 acute lymphoblastic leukemia

 

An adjunct to conventional chromosome studies in patients with T-cell acute lymphoblastic leukemia

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

In the United States, the incidence of acute lymphoblastic leukemia (ALL) is roughly 6,000 new cases per year (as of 2009), or approximately 1 in 50,000. ALL accounts for approximately 70% of all childhood leukemia cases (ages 0 to 19 years), making it the most common type of childhood cancer. Approximately 85% of pediatric cases of ALL 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 (LBL), approximately 90% are T-cell lineage versus only 10% B-cell lineage. T-LBL often present as a mediastinal mass in younger patients with or without concurrent bone marrow involvement.

 

Specific genetic abnormalities are identified in the majority of cases of T-ALL, although many of the classic abnormalities are "cryptic" by conventional chromosome studies and must be identified by 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 clone for the prognostic genetic subgroups. A summary of the characteristic chromosome abnormalities identified in T-ALL are listed in the following Table.

 

Cytogenetic change

Genes involved

del(1p32)

STIL/TAL1

t(5;14)(q35;q32)

TLX3(HOX11L2)/BCL11B

t(10;11)(p13;q14)

MLLT10(AF10)/PICALM

Episomal amplification

ABL1

del(9p)

CDKN2A(p16)

t(11q23;var)

MLL

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)(p13;q23)

MLLT10(AF10)/MLL

t(11;19)(q23;p13.1)

MLL/ELL

t(11;19)(q23;p13.3)

MLL/MLLT1(ENL)

t(7q34;var)

TRB

t(6;7)(q23;q34)

MYB/TRB

t(7;10)(q34;q24)

TRB/TLX1(HOX11)

t(7;11)(q34;p15)

TRB/LMO1

t(7;11)(q34;p13)

TRB/LMO2

t(14q11.2;var)

TRAD

t(8;14)(q24.1;q11.2)

MYC/TRAD

t(10;14)(q24;q11.2)

TLX1(HOX11)/TRAD

t(11;14)(p15;q11.2)

LMO1/TRAD

t(11;14)(p13;q11.2)

LMO2/TRAD

del(17p)

TP53

Complex karyotype (> or =4 abnormalities)

 

 

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 neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal reference range for any given probe.

 

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 should not be ordered on blood and bone marrow specimens from patients with T-cell lymphoma. In these situations, order FRTLP / T-Cell Lymphoma, FISH, Blood or Bone Marrow.

 

This test is not FDA approved and it is best used as an adjunct to existing clinical and pathologic information.

 

Bone marrow is the preferred specimen type for this FISH test. If bone marrow is not available, a blood specimen may be used if there are malignant cells in the blood specimen (as verified by hematopathology).

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. Edited by ES Jaffe, NL Harris, H Stein, JW Vardiman. Lyon, IARC Press, 2001

2. Gesk S, Martin-Subero JI, Harder L, et al: Molecular cytogenetic detection of chromosomal breakpoints in T-cell receptor gene loci. Leukemia 2003;17:738-745

3. Chin M, Mugishima H, Takamura M, et al: Hemophagocytic syndrome and hepatosplenic (gamma)(delta) T-cell lymphoma with isochromosome 7q and 8 trisomy. J Pediatr Hematol Oncol 2004;26(6):375-378

4. 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

5. Cayuela JM, Madani A, Sanhes L, et al: Multiple tumor-suppressor gene 1 inactivation is the most frequent genetic alteration in T-cell acute lymphoblastic leukemia. Blood 1996;87:2180-2186

6. Hayette S, Tigaud I, Maguer-Satta V, et al: Recurrent involvement of the MLL gene in adult T-lineage acute lymphoblastic leukemia. Blood 2002;99:4647-4649

7. Graux C, Cools J, Melotte C, et al: Fusion of NUP214 to ABL1 on amplified episomes in T-cell acute lymphoblastic leukemia. Nat Genet 2004;36:1084-1089

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test