Mammary tumor fibroblasts are phenotypically distinct from non-tumor fibroblasts

A tumor contains cellular and extracellular elements. Although breast tumors themselves are primarily of epithelial origin, these tumor cells do not exist in isolation, but require interaction with their surrounding environment including fibroblasts, fat cells, extracellular matrix and vascular elements. Traditionally, studies of tumor growth have focused on the malignant epithelial cells themselves. There is increasing evidence that there is a role for interaction between the tumor epithelium and stroma in the development and progression of breast cancer. This chapter focuses on the fibroblast component of mammary tumors: the signals they produce and their potential influence on the growth of the tumor itself.