Neoadjuvant chemotherapy is used in HER2-positive breast cancer to shrink the tumor and increase the chance of breast-conserving surgery. The article describes two cases of patients with this type of cancer who initially had palpable tumors in the breast confirmed by biopsy and frequent cells within cells (CIC). In the first patient after chemotherapy, there was a favorable pathological response associated with a decrease in the frequency of CIC. The other patient had only a limited response with persistent complex CICs, leading to a change in adjuvant therapy. These cases show different tumor responses to treatment depending on the dynamics of CIC. Observations suggest that CIC patterns may reflect diverse responses to neoadjuvant chemotherapy. This helps in planning individualized treatment.