Cancer Cytogenetics: Deep Roots, New Branches in the Age of Omics

For decades, the "death of cancer cytogenetics" has been repeatedly proclaimed and has grown louder in the era of omics. However, cytogenetics continues to evolve, retaining its central role in the study of chromosomes. From the microscopic visualization of numerical and structural aberrations using staining and banding techniques, the field has steadily incorporated new methodologies, including fluorescence in situ hybridization, array comparative genomic hybridization, high-throughput sequencing, and, most recently, optical genome mapping. These approaches have revealed unprecedented details of chromosome structure and behavior, uncovered catastrophic genomic events in cancer, and given rise to new concepts such as cytogenomics and chromosomics. Although cytogenetics is sometimes viewed as synonymous with chromosome banding, its scope, namely the study of chromosome structure and behavior, extends far beyond any single method. Chromosomes remain indispensable for understanding genome architecture, chromosomal instability, and fusion-gene mechanisms in neoplasia, irrespective of the technologies applied. Rooted in its past yet continually branching outwards with each scientific advance, today's cytogenetics integrates classical and modern approaches, carrying forward the legacy of chromosome banding while adopting genome-wide technologies. These developments underscore the enduring importance of cytogenetics for interpreting the structural complexity of cancer genomes. This review aims to demonstrate that cytogenetics, far from being obsolete, remains a vital component of modern cancer research by highlighting essential insights into chromosome structure, genome architecture, and fusion-gene mechanisms in the era of -omics.