ERBB2 and breast cancer: To examine the GHIST model in practice, we applied the model in its default single-cell expression setting directly to two external datasets: (1) a public TCGA-BRCA HER2-positive cohort consisting of 92 individuals and a TCGA-BRCA luminal cohort consisting of 461 individuals (defined by patient metadata; Methods), and (2) an in-house breast cancer tissue data consisting of 44 individuals.