The simultaneous occurrence of primary gastric cancer and breast cancer is rare, and the positive expression of human epidermal growth factor receptor (HER)2 in double primary carcinoma of gastric and breast cancer remains to be reported. The present study presented a 46-year-old woman complaining of irregular acid reflux and stomach discomfort. The stomach cancer was diagnosed by esophagogastroduodenoscopy examination of the pathological biopsies in 2010. The patient underwent a radical gastrectomy for gastric cancer, and postoperative pathological examination revealed moderately-poorly differentiated adenocarcinoma with HER2 positive expression. The tumor invaded into the entire thickness of the gastric wall and lymph nodes. The patient received five treatments of postoperative chemotherapy. In August 2011, the patient felt a lump in the right breast. Simple excision of the right breast mass was performed on September 2011, and postoperative pathological examination revealed the invasive ductal carcinoma of the right breast with HER2 amplification by fluorescent in situ hybridization assay. The patient was treated with postoperative chemotherapy and radiotherapy, and also Trastuzumab target therapy. The patient succumbed to aggressive disease progression in March 2012.
Keywords: HER2 positive; breast cancer; double primary carcinoma; gastric cancer.