PGR and neoplasm: Using univariate binary logistic regression analysis, younger age (p = 0.018), low histological grade (p = 0.002), tumor multiplicity (p = 0.001), ER positivity (p = 0.001), PR positivity (p = 0.049), and low Ki-67 proliferation index (p = 0.025) were confirmed to be predictors of HER2-zero to low conversion in surgical resection specimens (Table 5).