Every living species has a unique set of chromosomes that carry the necessary and sufficient genetic information to survive and reproduce. In order for living organisms to reproduce, it is very important that they correctly transfer their genetic information to new generations of cells. Here, defects in DNA replication, defects in cell cycle progression and control points, repair of DNA damage, correct and balanced separation of chromosomes are important. An error in any of these genetic pathways can lead to cell death or the formation of cells with altered genetic information. Since this situation changes the expression of genetic information significantly, it causes the development of pathological defects in the embryo or organism. The numerical chromosome abnormalities (NCAs) occurring in the organism are defined as aneuploidy. Cancer-related genetic events; it is unknown how activation of oncogenes and inactivation of tumor suppressors occurs with genes on the X chromosome. The molecular basis for the oncogenic effects of doubling the copy number of the genes that are affected is also unclear. But, the X-chromosome aneusomy is thought to have a possible role in neoplastic transformation. The X-chromosome monosomy provides a unique genetic gain for the expression of common cancer-causing genetic events. In this review, we explain the unique features of X chromosome with the features of cancer biology.