Repeated changes of the molecular subtype in gastric metastasis from breast cancer: A case report.

Gastric metastasis from breast cancer is clinically diagnosed rarely. The present study described an interesting and valuable case of gastric metastasis from breast cancer, which showed repeated changes of the molecular subtype with an impact on the choice of treatment. A 42-year-old woman underwent mastectomy with axillary lymph node dissection for an invasive lobular carcinoma of the left breast. The patient received gastroscopy due to an epigastric pain during the adjuvant chemotherapy. The endoscopic examination revealed an erosive lesion at the posterior wall of the gastric body. The gastric lesion was immunohistochemically diagnosed as a metastatic disease from the breast cancer. The patient initially received hormone therapy, according to the subtype of the primary and the metastatic diseases. The gastric lesion initially disappeared; however, a relapsed lesion transformed into luminal human epidermal growth factor receptor 2 type from luminal type. Subsequently, the metastatic lesions underwent repeated subtype changing, which created difficultly when deciding the treatment strategy. The molecular profile of breast cancer can change during the treatment, resulting in the treatment resistance observed in certain cases. Therefore, the optimal treatment must be selected, according to the changed subtype.