SPP1 and breast cancer: Many of these changes were consistent with increased deposition of collagen associated with high breast density [27], the development of large fibrotic foci and early metastases in hormone receptor-negative breast cancer [11], identification of CD52, Spp1 and Cxcl14 in the stromal gene expression signature in breast cancer subjects [30], and the greater expression of Spp1 in HER2+ and triple-negative breast cancer [34].