ESR1 and carcinoma: When the ERα-positive cases were further divided into separate classes based on the percentage of carcinoma cells stained (<1%, 1–5, 5–25 and >25% positive cells), the four curves showed significantly progressively poorer survival (Figure 3C; log rank test, P=0.006; Wilcoxon test χ2=10.12, 3 d.f., P=0.02).