Duodenal Adenocarcinoma Metastatic to the Breast: A Case Report.

Duodenal adenocarcinoma, a very rare malignant gastrointestinal tumor, mainly metastasizes via the lymphatic system. Metastases from duodenal adenocarcinomas to the breast are very uncommon. A 31-year-old woman presented at our department with a left breast tumor. She had a past medical history of duodenal adenocarcinoma. Physical examination on admission confirmed a 2.5-cm-diameter tumor in the outer lower quadrant of the left breast. Computed tomography (CT) examination showed a soft lesion with tissue-like density and enlarged axillary lymph nodes. Local excision was performed to remove the breast lesion. The findings of cytologic, histologic, and immunohistochemistry examination indicated a breast metastasis from the previous duodenal adenocarcinoma. The patient was treated with palliative chemotherapy. Metastases from duodenal adenocarcinoma to the breast are rare. The diagnosis depends on medical history, imaging, and pathologic examination including immunohistochemistry. An accurate diagnosis is important to avoid unnecessary surgery.