FISH, CLL, ATM, Deletion 11q22.3

Laboratory assay overview

This fluorescence in situ hybridization (FISH) assay detects deletion of the ATM gene region in chromosome 11q22.3. The results of this test may aid in the prognostic assessment and treatment selection for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). The most common genetic abnormalities of CLL/SLL are del(13q), del(11q), trisomy 12, and del (17p). At least one of these 4 genetic abnormalities can be detected with FISH in >80% of patients with CLL/SLL [1]. Evaluation of these frequent genetic abnormalities is recommended for the investigation of prognosis [2] and may inform treatment decisions [3]. Del(11q) results in the loss of the ATM gene and can be detected with FISH in 18% of patients with CLL/SLL [1]. The presence of del(11q) is associated with marked lymphadenopathy and unfavorable prognosis [2,3]. A combination of genetic techniques is often involved in identifying genetic abnormalities. FISH testing is complementary to conventional cytogenetic analysis (karyotyping) and can be used to detect common cytogenetic abnormalities. However, because FISH is limited to probing specific chromosomal regions, it does not replace conventional cytogenetic analysis or chromosomal microarray for screening unknown abnormalities. The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Dohner H, et al. N Engl J Med. 2000;343(26):1910-1916. 2. Naresh KN, et al. B-cell lymphoid proliferations and lymphomas. In: WHO Classification of Tumours Editorial Board. The World Health Organization Classification of Haematolymphoid Tumours. 5 Beta V2 ed. IARC Press; 2022:chap 4. Accessed June 16, 2023. https://tumourclassification.iarc.who.int 3. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®). Chronic lymphocytic leukemia/small lymphocytic lymphoma. Version 3.2023. Updated June 12, 2023. https://www.nccn.org