ESR1 and neoplasm: The NbClust algorithm identified four clusters in the data set that were significantly associated with the ER status (P < 0.001), the PR status (P < 0.001), the HER2 status (P = 0.043), the ER/HER2 combined subtypes (P < 0.001), and the IBC/nIBC tumor phenotype (P < 0.001).