ERBB2 and breast carcinoma: Interestingly, however, the HyperZ index was not only highest in luminal B tumors, but also in the HER2+ subtype, whereas the HypoZ index was significantly lower in HER2+ tumors compared with luminal B. Thus, this shows that luminal B breast cancers exhibit more widespread deregulation of DNAm patterns than HER2+ breast cancers.