This image represents a mixture of different types of breast cancer cells residing within a tumor and their interaction with immune cells. Most breast tumors are comprised of breast cancer cells along with cells of the immune response. These immune cells greatly influence the ability of breast tumors to spread to distant sites of the body. In this image one can observe a specific subset of immune cells called macrophages in red, interacting with two different types of breast cancer cells depicted in white and blue. The macrophages are found in larger numbers in the mesenchymal (green) section of the tumor relative to the epithelial (white) sections in the same tumor.