Cancer is a disease, result of different mutations caused in the genes which are regulating cell-growth. As a result of these mutations in the genes, cells are dividing in an uncontrolled manner. Cancer of the breast occurs when it starts in breast cells. Epigenetic, transcriptional, post-transcriptional, and post-translational processes all play roles in controlling PTEN gene expression in cells. Both the PTEN gene (at position q23.3) and the PTENP1 gene (at position p33.3) may be found on chromosome 9. The phosphatase and tensin homolog (PTEN) gene acts as a tumor suppressor. In addition to the processed pseudogene PTENP1 (Phosphatase and Tensin Homolog Pseudogene 1) and PTEN-targeting short noncoding RNAs like microRNAs (miRNAs), PTEN gene expression is controlled by sense and antisense transcripts of the PTENP1 long noncoding RNA. Several transcription factors attach to the PTEN gene promoter in order to activate or inhibit transcription. Some short non-coding RNAS miRNAs regulate PTEN gene expression post-transcriptionally by inhibiting translation at the 3'-untranslated region (3'UTR).