Since 1990, our research is focused over an emerging issue related to the importance of stromal microenvironment in the development of breast cancer. It is well known that the approach of this disease based exclusively on the intrinsic properties of tumor cells is insufficient. The environment surrounding the tumor cells must be considered not only in the primary tumor but also in the pre-metastatic niche. Our data demonstrated that the hematopoietic microenvironment of bone marrow, particularly mesenchymal stem cells, from patients with advanced breast cancer favored the formation of a suitable pre-metastatic niche for the tumoral colonization in the bone marrow and bone. Moreover, the study of this type of stem cells in the environment of primary tumor from breast cancer patients in early clinico-pathological stages allowed us to identify new biomarkers predictors of metastasis, especially in the bone, and lower survival. We believe that our results supply new information about the changes that occur mainly in the bone marrow of these advanced breast cancer patients previous to the development of bone metastases; allowing to design innovative therapies in order to prevent or at least to delay the beginning of this type of metastasis, as well as design new strategies for early detection and diagnosis. On the other hand, we are studying the prognostic relevance of the microbiome in the evolution of early breast cancer. The particular objective of this subline is to identify the possible links between the composition of bacteria in the breast tumor microenvironment and the clinical characteristics, as well as to establish for the first time the possible associations between the microbiome (bacteria associated with parameters of good or bad prognosis ) and tumor progression in patients with early breast cancer. Research that in the future will give the possibility of developing new alternative therapies such as "probiotics" (using the microbiome with a good prognosis) that improve the quality of life of the patient.