Background: Complex genomic changes that arise in tumors are a consequence of chromosomal instability. In tumor cells genomic aberrations disrupt core signaling pathways involving various genes, thus delineating of signaling pathways can help understand the pathogenesis of cancer. The bioinformatics tools can further help in identifying networks of interactions between the genes to get a greater biological context of all genes affected by chromosomal instability. Results: Karyotypic analyses was done in 150 clinically confirmed breast cancer patients and 150 age and gender matched healthy controls after 72 hours Peripheral lymphocyte culturing and GTG-banding. Karyotypic analyses found more frequent chromosomal aberrations (structural and numerical) on chromosome 1, 2, 3, 4, 5, 8, 9, 17 and X. The data of genes harbored by chromosomal regions showing increased aberration frequency was retrieved from online databases. Pathway analysis on a set of genes that were not linked together revealed that genes HDAC3, NCOA1, NLRC4, COL1A1, RARA, WWTR1, and BRCA1 were enriched in the RNA Polymerase II Transcription pathway which is involved in recruitment, initiation, elongation and dissociation during transcription. Conclusion: The chromosomal instability analysis in a non-target in cancer patients thus can be used to identify genes and decipher the pathway involved in tumorigenesis. The bioinformatics approach can help in identifying aberrant genes in transcription pathways and their relation with breast cancer progression.