BCR/ABL, T(9;22) TRANSLOCATION BY DUAL FUSION FISH

Code
000.0000
Name
BCR/ABL, T(9;22) TRANSLOCATION BY DUAL FUSION FISH
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
Philadelphia Chromosome; abelsone oncogene; bcr
CPT Codes
88271 x3; 88275; Genetic testing code modifier 2B may be added to the above CPTs if required by the payer
Site
GenPath
Reference Test
ATLAS Test Code

Specimen Information

Type

Lavender top (EDTA) tube, BONE MARROW or WHOLE BLOOD

Volume

1.0 mL bone marrow - OR - 5.0 mL whole blood

Transport Info

Room Temperature

Fasting Required?
False
Patient Instructions

Reference Range

See Report

Methodology

Dual Fusion Fluorescence In Situ Hybridization (D-FISH)

Clinical Significance

Aid in the diagnosis of Chronic Myelogenous Leukemia (CML)

More than 90% of patients with Chronic Myelogenous Leukemia (CML) have a proliferation of cells in their bone marrow and blood which show t(9:22)(q34;q11.2) – often called the Philadelphia Translocation. This translocation is also observed in 3% of children and 20% of adults with Acute Lymphoblastic Leukemia (ALL), as well as in 1% of patients with Acute Myeloid Leukemia (AML). The balanced translocation between chromosomes 9 and 22 involves the Abelson (ABL) oncogene at 9q34 and the breakpoint cluster region (BCR) at 22q11.2. In CML, the hybrid BCR/ABL gene is always present and the abnormal chimeric protein has increased tyrosine kinase activity. In a minority of cases, the breakpoint in the BCR gene can occur in a minor region.Fluorescent in Situ Hybridization (FISH) methods permit visualization of BCR/ABL fusion in individual interphase and metaphase cells. A tricolor, dual fusion FISH method detects BCR/ABL fusion in cells, deletion on derivative chromosome 9 and chromosome 22, and deletion of arginisosuccinate synthetase (ASS) gene which is located at chromosome 9q34. Deletion of ASS is an indicator of a subclone of cells within the Philadelphia positive cells that may be changing or mutating. This indicator has been associated with poor prognosis.In classic CML, the presence of the translocation or the BCR/ABL fusion establishes the diagnosis and predicts the transformation into blast crisis (accelerated phase). FISH confirmation or exclusion of CML in suspected cases is critical to allow tailored therapy. Testing must quantify the abnormal cells before and after treatment to help assess effectiveness of therapy. Low levels of abnormal cells predict relapse early and lead to revision of therapy. With conventional cytogenetics methods, evidence of translocation or low levels of mosaicism may be missed.

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