Gastrointestinal metastasis from invasive lobular carcinoma following breast cancer treatment: A case report.

Background: Metastasis of breast cancer usually affects the lungs, bones, liver, and brain. It rarely spreads to the gastrointestinal tract, and cases with similar endoscopic manifestations are even rarer. Herein, we report a 52-year-old woman presenting with metastatic lobular carcinoma involving the gastrointestinal tract four years following a left mastectomy, chemoradiotherapy, and hormone therapy for lobular carcinoma of the breast.

Case summary: A 52-year-old woman presented with a history of invasive lobular carcinoma and experienced metastasis of breast cancer to the gastrointestinal tract. The patient underwent a left mastectomy and tumor cells were positive for estrogen receptor (ER) and progesterone receptor (PR), negative for human epidermal growth factor receptor 2 (HER2) and E-cadherin. She did not experience any local or distant recurrences for four years following the mastectomy, chemoradiotherapy, and hormone therapy. However, the patient complained of upper abdominal discomfort and was transferred to our hospital. The endoscopic examination revealed multiple crater-like ulcers scattered throughout the stomach, gastric antrum, and colorectum. Surprisingly, the histology of colorectum lesions was the same as that of gastric metastasis. Gastric tumor cells were positive for GATA-binding protein 3 (GATA3), PR, and ER, negative for HER2. The colorectum tumor cells were positive for GATA3 and ER and negative for cytokeratin 20. Based on the results of immunohistological examination, a final diagnosis of gastrointestinal metastases from breast cancer was established.

Conclusion: Distinguishing metastatic breast cancer from primary gastrointestinal lesions is crucial for initiating the correct treatment and enhancing the quality of life for patients.