Table 1.

The advantages and deficiencies of the breast models in breast tumor-on-a-chip.

Model Type		Advantages	Deficiencies	Reference
spheroid model	Homotypic spheroid model	simple, diversified preparation technology, easy to prepare, efficient, controllable	monotony, very different from the real situation in body	[75,76,77]
	Heterotypic spheroid model	simulate the tumor tissue in the body more realistically	co-cultivation dilemma, low efficiency
lumen model	Breast ductal model	enable simulation of breast duct structure and function	dependence on the scaffold and self-organization, low efficiency	[42,78,79]
	Breast-vasculature model	enable simulation of the infiltration and extravasation of the cancer invasion
other patterned models		designable	high dependence on the scaffold, low efficiency	[46,49]
breast-other organ model		complex, diverse, simulates the interaction between tissues and organs in vitro, close to in vitro body model	co-cultivation dilemma, low efficiency	[51,52,53]
hypoxia model		simulates the hypoxia microenvironment around the tumor in body, diversified methods, controllable	difficult to prepare, severely affected by airtightness and matrix permeability	[74,80,81]