ERBB2 and breast cancer: Further analysis of the prevalence of PTENalt (homozygous loss, missense mutations, or truncations) and PTEN hemizygous loss in ER+/HER2- BC biopsies harbouring different PIK3CA activating mutations present in different exons showed that co-occurrent PTEN alterations like mutations, truncations, homo- or hemizygous deletions are common (Fig. 2C and Supplementary Table 1).