Conlin, Laura K.

Abstract Background Genetic testing has traditionally been divided into molecular genetics and cytogenetics, originally driven by the use of different assays and their associated limitations. Cytogenetic technologies such as karyotyping, fluorescent in situ hybridization or chromosomal microarrays are used to detect large “megabase level” copy number variants and other structural variants such as inversions or translocations. In contrast, molecular methodologies are heavily biased toward subgenic “small variants” such as single nucleotide variants, insertions/deletions, and targeted detection of intragenic, exon level deletions or duplications. The boundaries between these approaches are now increasingly blurred as next-generation sequencing technologies and their use for genome-wide analysis are used by both disciplines, therefore eliminating the historic and somewhat artificial separation driven by variant type. Content This review discusses the history of genomic nomenclature across both fields, summarizes implementation challenges for the clinical genetics community, and identifies key considerations for enabling a seamless connection of the stakeholders that consume variant descriptions. Summary Standardization is naturally a lengthy and complex process that requires consensus building between different stakeholders. Developing a standard that not only fits the multitude of needs across the entities that consume genetic variant information but also works equally well for all genetic variant types is an ambitious goal that calls for revisiting this vision.

Context.— One goal of the joint College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee is to ensure the accurate detection and description of chromosomal abnormalities in both constitutional and neoplastic specimens, including hematologic neoplasms. Objective.— To report a 20-year performance summary (1999–2018) of conventional chromosome challenges focusing on hematologic neoplasms. Design.— A retrospective review was performed from 1999 through 2018 to identify karyotype challenges specifically addressing hematologic neoplasms. The overall performance of participants was examined to identify potential recurring errors of clinical significance. Results.— Of 288 total conventional chromosome challenges from 1999–2018, 87 (30.2%) were presented in the context of a hematologic neoplasm, based on the provided clinical history, specimen type, and/or chromosomal abnormalities. For these 87 hematologic neoplasm challenges, 91 individual cases were provided and graded on the basis of abnormality recognition and karyotype nomenclature (ISCN, International System for Human Cytogenomic [previously Cytogenetic] Nomenclature). Of the 91 cases, 89 (97.8%) and 87 (95.6%) exceeded the required 80% consensus for grading of abnormality recognition and correct karyotype nomenclature, respectively. The 2 cases (2 of 91; 2.2%) that failed to meet the 80% consensus for abnormality recognition had complex karyotypes. The 4 cases (4 of 91; 4.4%) that failed to meet the 80% consensus for correct karyotype nomenclature were the result of incorrect abnormality recognition (2 cases), missing brackets in the karyotype (1 case), and incorrect breakpoint designation (1 case). Conclusions.— This 20-year review demonstrates clinical cytogenetics laboratories have been and continue to be highly proficient in the detection and description of chromosomal abnormalities associated with hematologic neoplasms.