Human Epidermal Growth Factor Receptor 2-Positive Duodenal Adenocarcinoma: A Case Report and Review of the Literature.

Duodenal adenocarcinoma is a rare malignancy and carries a poor prognosis. The role of adjuvant therapy and the optimal chemotherapy regimen remain largely unclear. Treatment with trastuzumab results in prolonged survival in gastroesophageal cancer if human epidermal growth factor receptor 2 (HER2) is overexpressed or amplified in tumor cells. However, unlike gastric adenocarcinomas, duodenal cancers seem to rarely harbor HER2 amplification or overexpression. We report the case of a patient with HER2-positive stage III duodenal adenocarcinoma who has received adjuvant chemotherapy including trastuzumab.