<i>diazotrophicus</i> in an elderly female breast cancer patient with chemotherapy-induced febrile neutropenia.<h4>Case presentation</h4>A 62-year-old woman with HER2-positive, cT4bN2M0 breast cancer receiving neoadjuvant trastuzumab, carboplatin, and docetaxel presented with fever, headache, profound fatigue, pallor, and retinal hemorrhages. Here, ERBB2 is linked to breast cancer.