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Issue 240: Spatial divergence is an important perspective of intra-tumour heterogeneity. Much interesting work has been done to measure how mutation accumulation diverges over space. Using an agent-based model, we apply the Jaccard index to compare the portion of shared mutations between samples while varying the sampling distance and tumour expansion modes. We infer mutation rates based on the distributions of variant allele frequencies under different tumour expansion modes and sampling sizes. In exponentially fast expanding tumours, a mutation rate can always be inferred in any sampling size. However, the accuracy compared to the true value decreases when the sampling size decreases, where small sampling sizes result in a high estimate of the mutation rate. Such an inference becomes unreliable when the tumour expansion is slower e.g. in surface growth. To learn more, click here.