Rationale:
Advanced breast cancer frequently metastasizes to the lungs, liver, and bones. Metastatic involvement of the duodenal bulb is extremely rare and difficult to detect by endoscopy.
Patient concerns:
A 51-year-old menopausal woman presented with abdominal fullness and obstructive symptoms, and was diagnosed with adenocarcinoma in the duodenal bulb. The patient had undergone modified radical mastectomy of the left breast for infiltrating ductal carcinoma (IDC) 8 years previously.
Diagnosis:
Metastatic infiltration of the duodenal bulb originating from IDC was proven histologically and immunohistochemically.
Interventions:
She received chemotherapy with docetaxel and capecitabine followed by hormone maintenance therapy with letrozole after operation.
Outcomes:
After treatment, the patient recovered well. She is currently being followed up.
Lessons:
Patients with known breast cancer history with the IDC histological type and presenting with nonspecific abdominal symptoms or signs, such as abdominal fullness, nausea, and vomiting, should undergo endoscopy with histopathological examination in order to detect possible gastrointestinal metastasis of the primary breast tumor. This report intends to alert people to heed this type of breast cancer metastasis and not treat it as a primary gastrointestinal tumor.