Fig. 1From: Small extracellular vesicles: from promoting pre-metastatic niche formation to therapeutic strategies in breast cancerFormation of PMNs. The PMNs in cancer can be divided into three major temporal phases following a sequential order. First, the metastatic microenvironment is deternmined by the primary tumour. Second, the secondary sites recruit immunosuppressive cells. Finally, circulating tumour cells invade and colonize distant organs or tissuesBack to article page