Fig 2. Hanging drop spheroid (HDS) simulations with deterministic necrosis (left) and stochastic necrosis (right), plotted at 4, 8, and 16 days.

Videos are available at S1 and S2 Videos. Legend: Ki67+ cells are green before mitosis (K₁) and magenta afterwards (K₂). Pale blue cells are Ki67- (Q), dead cells are red (apoptotic) and brown (necrotic), and nuclei are dark blue. Bottom: Hanging drop spheroid experiment (HCC827 non-small cell lung carcinoma) showing a similar necrotic core microstructure. PhysiCell is the first simulation to predict this structure arising from cell-scale mechanical interactions. Image courtesy Mumenthaler lab, Lawrence J. Ellison Center for Transformative Medicine, University of Southern California.