The metastatic dissemination of cancer cells from primary tumors to secondary loci is a complex and multistep process including local invasion, intravasation, survival in the blood stream and extravasation towards the metastatic site. It is well known cancer metastases follow organ-specific pathways with selected primary tumors mainly metastasizing towards a specific panel of secondary organs (Steven Paget's theory 1889). However, circulatory patterns and microarchitecture of capillary networks play a key role in the metastatic spread as well (James Ewing's theory 1929). Taking into account both these factors would be critical to develop more complex and physiologically relevant in vitro cancer models. This review presents recent advances in the generation of microvascularized systems through microfluidic approaches and discusses promising results achieved by organ-on-a-chip platforms mimicking the pathophysiology of the functional units of specific organs. The combination of physiologically-like microvascular networks and organotypic microenvironments would foster a new generation of in vitro cancer models to more effectively screen new therapeutics, design personalized medicine treatments and investigate molecular pathways involved in cancer metastases.