A Case of Minimally Invasive HER2-Positive Breast Cancer Metastasizing to the Lung after Surgery

Abstract

Breast tumors are pathologically classified as invasive breast cancer, non-invasive breast cancer, Paget disease, and minimally invasive breast cancer (defined as invasive size <1 mm breast cancer). The prognosis for minimally invasive breast cancer has been reported to be similar to that of non-invasive breast cancer ; however, distant metastasis can occur. As clinical trials that provide the basis for this evidence have been limited to patients with tumors ≥ 1 cm in diameter, patients with minimally invasive breast cancer have received no adjuvant treatment. In this case report, we present a patient who developed a lung metastasis 12 months following curative breast surgery. The patient underwent partial lobectomy for the solitary metastatic lung lesion, and the resected tumor revealed metastatic HER-2 positive breast cancer. The patient received anti-HER-2 treatment without recurrence to date. This is a rare case of HER-2 positive minimally invasive breast cancer metastasizing to the lung that was successfully removed, which we present along with a review of the literature.