An increasing body of evidence supports a stepwise model for progression of breast cancer from ductal carcinoma in situ(DCIS) to invasive ductal carcinoma(IDC). Due to the high level of DCIS heterogeneity, we cannot currently predict which patients are at highest risk for disease recurrence or progression. The mechanisms of progression are still largely unknown, however cancer stem cell populations in DCIS lesions may serve as malignant precursor cells intimately involved in progression. While genetic and epigenetic alterations found in DCIS are often shared by IDC, m RNA and mi RNA expression profiles are significantly altered. Therapeutic targeting of cancer stem cell pathways and differentially expressed mi RNA could have significant clinical benefit. As tumor grade increases, mi RNA-140 is progressively downregulated. mi R-140 plays an important tumor suppressive role in the Wnt, SOX2 and SOX9 stem cell regulator pathways. Downregulation of mi R-140 removes inhibition of these pathways, leading to higher cancer stem cell populations and breast cancer progression. mi R-140 downregulation is mediated through both an estrogen response element in the mi R-140 promoter region and differential methylation of Cp G islands. These mechanisms are novel targets for epigenetic therapy to activate tumor suppressor signaling via mi R-140. Additionally, we briefly explored the emerging role of exosomes in mediating intercellular mi R-140 signaling. The purpose of this review is to examine the cancer stem cell signaling pathways involved in breast cancer progression, and the role of dysregulation of mi R-140 in regulating DCIS to IDC transition. An increasing body of evidence supports stepwise model for progression of breast cancer from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). Due to the high level of DCIS heterogeneity, we can not currently predict which patients are at highest risk for The mechanisms of progression are still largely unknown, however cancer stem cell populations in DCIS lesions may serve as malignant precursor cells intimately involved in progression. While genetic and epigenetic alterations found in DCIS are often shared by IDC, m RNA and Therapeutic targeting of cancer stem cell pathways and differentially expressed mi RNA could have significant clinical benefit. mi R-140 plays an important tumor suppressive role in the Wnt, SOX2 and SOX9 stem cell regulator pathways. Downregulation of mi R-140 removes inhibition of these pathways ways, leading to higher cancer stem cell populations and breast cancer progression. mi R-140 downregulation is mediated through both an estrogen response element in the mi R-140 promoter region and differential methylation of Cp G islands. These mechanisms are novel targets for epigenetic therapy to activate tumor suppressor signaling via mi R-140., briefly explored the emerging role of exosomes in mediating intercellular mi R-140 signaling. The purpose of this review is to examine the cancer stem cell signaling pathways involved in breast cancer progression , and the role of dysregulation of mi R-140 in regulating DCIS to IDC transition.