HER2-Positive Right Breast Cancer With Complete Response Before Bilateral Mastectomy

What happened, in summary

A 59-year-old woman was evaluated for right-sided breast pain. Imaging found a roughly 3 cm right-breast mass, and biopsy confirmed grade 3 invasive ductal carcinoma. The tumor was ER negative, PR negative and HER2 positive, with Ki67 at 67%. A right axillary-node biopsy showed no malignancy. She received neoadjuvant carboplatin-based chemotherapy with Herceptin. After treatment, bilateral mammography showed complete resolution of the known right-breast mass. At her request, she then underwent bilateral total mastectomy, right sentinel lymph-node biopsy and immediate reconstruction. Pathology found no residual tumor in the right-breast specimen, and the right sentinel lymph node was negative. This supports a strong treatment response for the right-sided cancer. The operation unexpectedly found a separate cancer in the left breast with a different receptor profile. The right-sided cancer itself showed no residual tumor after treatment and surgery.