Chronic Lymphocytic Leukemia (CLL), FISH
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in North America. Certain cytogenetic abnormalities, gene mutations, and protein products contribute to disease progression and survival in B-CLL, but the primary oncogenic event is unknown. The most common cytogenetic anomalies in B-CLL involve chromosomes 6, 11, 12, 13, and 17. Use of CpG-oligonucleotide mitogen (CPG/89090 Chromosome Analysis, CpG Mitogen Study for B-Cell Disorder) will identify an abnormal CLL karyotype in at least 80% of cases. Unstimulated conventional chromosome studies (BM/8506 Chromosome Analysis, Hematologic Disorders, Bone Marrow and HBL/8537 Chromosome Analysis, Hematologic Disorders, Blood) are usually not successful for B-cell CLL. Molecular genetic analyses of patients with B-CLL are problematic, as these studies are hampered by the presence of nonclonal cells and by limited knowledge of candidate genes. Methods using chromosome-specific fluorescent-labeled DNA probes and FISH permit detection of various trisomies, deletions, and translocations in nondividing cells of patients with B-CLL. Disease can be quantified before and after therapy.
This test detects abnormal clones in approximately 60% of patients with indolent disease and >80% of patients that require treatment (see Supportive Data). At least 7% of patients referred for CLL FISH testing have translocations involving the IgH locus; approximately 77% of these patients have translocations that result in fusion of IGH/CCND1, IGH/BCL2, or IGH/BCL3. The CCND1, BCL2, and BCL3 genes are located on chromosome 11, 18, and 19, respectively. Fusion of IGH and CCND1 is associated with t(11;14)(q13;q32), IGH and BCL2 with t(14;18)(q32;q21), and IGH and BCL3 with t(14;19)(q32;q13.3). Patients with t(11;14)(q13;q32) usually have the leukemic phase of mantle cell lymphoma, while patients with t(14;18)(q32;q21) or t(14;19)(q32;q13.3) have an atypical form of B-CLL or the leukemic phase of a lymphoma.
Chromosome anomalies detected by this FISH assay reportedly are associated with prognosis, in a hierarchy, from best to worst prognosis, as follows:13q-, normal, +12, 6q-, 11q-, and 17p-.
Detecting clones with abnormalities of chromosomes 6, 11, 12, 13, 14, 17, 18, or 19 in patients with B-cell chronic lymphocytic leukemia (B-CLL)
Quantifying disease before and after therapy in patients with B-CLL
Distinguishing patients with 11;14 translocations who have leukemic phase of mantle cell lymphoma from patients who have B-CLL
Detecting patients with atypical B-CLL or other forms of lymphoma associated with 14;18 or 14;19 translocations
A neoplastic clone is detected when the percent of cells with any given chromosome abnormality exceeds the normal reference range. Normal cutoff (based on upper boundary for a 95% confidence interval):
Deletion in 6q, 11q, 13q, or 17p
<6.5%, <5.0%, <7.0%, and <8.5%, respectively
Trisomy 6, 11, 12, 13, 17, 18, or 19
Translocations involving the IgH locus
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
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. Dewald GW, Brockman SR, Paternoster SF, et al: Chromosome anomalies detected by interphase FISH: correlation with significant biological features of B-cell chronic lymphocytic leukemia. Brit J Haematol 2003;121:287-295
2. Nowakowski GS, Dewald GW, Hoyer JD, et al: Interphase fluorescence in situ hybridization with an IGH probe is important in the evaluation of patients with a clinical diagnosis of chronic lymphocytic leukaemia. Br J Haematol. 2005 Jul;130(1):36-42
3. Shanafelt TD, Witzig TE, Fink SR, et al: Prospective Evaluation of Clonal Evolution During Long-Term Follow-Up of Patients With Untreated Early-Stage Chronic Lymphocytic Leukemia. J Clin Oncol 2006;24: 4634-4641
4. Dohner H, Stilgenbauer S, Benner A, et al: Genomic aberrations and survival in chronic lymphocytic leukemia. N Engl J Med 2000 Dec;343(26):1910-1916
5. Stockero KJ, Fink SR, Smoley SA, et al: Metaphase cells with normal G-bands have cryptic interstitial deletions in 13q14 detectable by fluorescence in situ hybridization in B-cell chronic lymphocytic leukemia. Cancer Genet Cytogenet 2006;166:152-156
6. Van Dyke DL, Shanafelt TD, Call TG, et al: A comprehensive evaluation of the prognostic significance of 13q deletions in patients with B-chronic lymphocytic leukaemia. Br J Haematol 2010;148:544-50