A lower proportion of young adult patients had lobular carcinoma (2.1%), HR−/HER2+ expression (7.9%), surgery only (4.2%), and BMI ≥ 24 kg/m2 (28.3%), whereas a higher proportion had surgery combined with adjuvant and neoadjuvant therapy (11.3%), underweight BMI (10.8%), current cigarette smoking status (6.6%), and current casual alcohol drinking status (5.0%). Here, ERBB2 is linked to breast lobular carcinoma.