Abstract
BACKGROUND: Breast cancer (BC) metastasis to the gastrointestinal tract is uncommon, colonic metastasis from BC (CMBC) is even rarer. CASE SUMMARY: This report describes a 44-year-old female patient with metastatic triple-negative BC in the ascending colon who underwent laparoscopic radical right hemicolectomy. The patient had undergone left modified radical mastectomy only 15 months ago and stopped chemotherapy just 3 months ago. The diagnosis of CMBC was made based on the previous history of BC and positive results of several specific immunohistochemical markers (gross cystic disease fluid protein 15, mammaglobin, GATA-binding protein 3, and cytokeratin 7) for breast carcinoma. CONCLUSION: CMBC should be highly cautious in patients with a previous history of BC, especially triple-negative BC, and further examination to aid in diagnosis.