ESR1 and breast ductal adenocarcinoma: As shown in Table 1, low cytoplasmic CYP2S1 was significantly associated with ER‐positive status (χ2 = 6.543, df = 1, p = 0.011), HER2‐negative disease (χ2 = 10.721, df = 1, p = 0.001), ≥50 years (χ2 = 11.496, df = 1, p < 0.001), grade 3 tumours (χ2 = 24.785, df = 2, p < 0.001), intermediate NPI prognostic group (χ2 = 12.138, df = 2, p = 0.002), high nuclear pleomorphism (χ2 = 11.566, df = 2, p = 0.003), mitosis (χ2 = 12.874, df = 2, p < 0.001), and ductal carcinomas (χ2 = 14.790, df = 6, p = 0.022).