Cancer cells’ ability to tolerate crowded conditions may be one key to understanding tumor growth and formation, according to a mathematical model that has been applied to cancer cell growth for the first time. The model can replicate patterns of melanoma cell growth seen in laboratory experiments by controlling the ‘exclusion area’—the amount of space required—around two types of simulated cells as they grow and spread. A paper describing the model and experiments appears in a recent issue of the journal Scientific Reports.