Macrophages, more than just scavengers: their role in breast development and cancer.

Macrophages, derived from circulating monocytes, are located within virtually all adult tissues. There, these specialized cells adopt tissue-specific functions that are important for normal tissue homeostasis and response to physiological challenges. Increasing evidence suggests that macrophages play a role in the normal development of certain organs, such as the breast. Intriguingly, macrophages are often found in the stroma of breast tumours, where they may promote tumour growth and metastasis. In this review we discuss this emerging area of developmental and tumour biology.