Introduction: The salivary duct carcinoma (SDC) is an uncommon aggressive malignant tumor of the salivary glands with frequent metastasis leading to a poor prognosis. SDC resembles high-grade breast ductal carcinoma and frequently overexpress human epidermal growth factor receptor-2 (HER-2). We report herein on a case of recurrent metastatic SDC treated with trastuzumab-based chemotherapy. A 77-year-old female was diagnosed as having a malignant tumor of the right parotid gland and underwent total parotidectomy and bilateral neck dissection. The resected tumor was histologically investigated and diagnosed as an SDC. No amplification of the HER-2 gene was found but overexpression of the HER-2 protein was detected (2+). Multiple metastases at the bilateral axillary and superior mediastinal lymph nodes were detected 10 months after surgery. We treated the patient with triweekly chemotherapy with a combination of trastuzumab and docetaxel for 4 cycles. However CT scan showed disease progression after chemotherapy. Conclusion: It is important to check out not only the overexpression of HER-2 protein with IHC, but HER-2 gene amplification also should be checked before trastuzumab-based chemotherapy for SDC.
