Cell morphology of cell lines grown in two-dimensional and three-dimensional cultures. Two-dimensional culture of (a) luminal A T47D and (b) HER2-positive MDA-MB-453 cell lines grown on tissue culture plastic. T47D cells demonstrate a tightly cohesive cobblestone appearance, whereas MDA-MB-453 cells have an elongated and spindly appearance. (c) T47D and (d) MDA-MB-453 cell lines cultured in three dimensions as previously described . T47D cells form tightly cohesive mass structures displaying robust cell-cell adhesions, whereas MDA-MB-453 cells form loosely cohesive grape-like structures consistent with morphology observed by Kenny and colleagues .