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Interpretive Handbook

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Test 88783:
T-Cell Acute Lymphoblastic Leukemia (T-ALL), FISH

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

T-cell malignancies account for approximately 12% of all non-Hodgkin lymphomas. There are several subtypes of T-cell neoplasms: T-cell acute lymphoblastic leukemia (T-ALL), T-cell prolymphocytic leukemia (T-PLL), T-cell large granular lymphocytic leukemia (T-LGL), anaplastic large cell lymphoma (ALCL), peripheral T-cell lymphoma, and various other cutaneous, nodal, and extranodal lymphoma subtypes. The 2 most prevalent lymphoma subtypes are unspecified peripheral T-cell lymphoma (3.7%) and ALCL (2.4%).

 

T-ALL is a neoplastic disorder of lymphoblasts committed to the T-cell lineage. These malignancies comprise 15% to 20% of acute leukemias. While half of T-ALL patients have normal chromosome studies, molecular cytogenetic analysis can identify abnormalities including:

-Cryptic deletions of CDKN2A.

-Rearrangements involving 1p32 (STIL/TAL1), 7q34 (TRB), 11q23 (MLL), and 14q11.2 (TRAD).

-Chromosomal translocations including t(5;14)(q35;q32), t(9;22)(q34;q11.2), t(10;11)(p13;q14), and various partner genes involved with the MLL and TRAD gene loci.

-Episomal amplification involving the ABL1/NUP214 fusion gene.

 

These abnormalities may be seen in tissues (ie, lymph nodes), as well as in blood and bone marrow. This assay detects the common chromosome abnormalities observed in T-ALL.

 

A few common chromosome abnormalities are associated with specific T-cell lymphoma subtypes, including:

-inv(14)(q11q32) and t(14;14)(q11;q32) involving the T-cell leukemia/lymphoma 1 gene (TCL1A) at 14q32

-Translocations involving the ALK gene at 2p23 in ALCL

-Isochromosome 7q and trisomy 8 in hepatosplenic T-cell lymphoma

 

For blood and bone marrow specimens from patients with T-cell lymphomas, see FRTLP/89040 T-Cell Lymphoma, FISH, Blood or Bone Marrow.

 

These probes have diagnostic relevance and can also be used to track response to therapy.

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

 

Tracking known chromosome abnormalities and response to therapy in patients with T-cell acute lymphoblastic leukemia

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.

 

Detection of an abnormal clone is supportive of a diagnosis of T-cell acute lymphoblastic leukemia (T-ALL). The specific anomaly detected may help subtype the neoplasm.

 

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/89040 T-Cell Acute 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.

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.

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

1. World Heath 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