Aneuploidy or alteration in chromosome numbers is a characteristic feature in cancer that is generally a consequence of defective chromosome segregation during cell division. Molecular cytogenetic analyses have conferred substantial evidence with regards to the chromosomal architectures in cancer. Most importantly, the fluorescence in situ hybridization (FISH) technique that plays a leading role in diagnostic pathology for its single-cell analysis has provided crucial information regarding genomic variations in malignant cells. Further development of molecular cytogenetic methodologies such as chromosome specific FISH karyotyping and comparative genomic hybridization have also helped in the detection of cryptic genetic changes in cancer. But, the recent advancement of high throughput sequencing technologies have provided a more comprehensive genomic analyses resulting in novel chromosome rearrangements, somatic mutations as well as identification of fusion genes leading to new therapeutic targets. This review highlights the application of early molecular cytogenetics and the recent high throughput genomic approaches in characterizing various cancers and their invaluable support in cancer therapeutics.