BACKGROUND: Breast cancer is the most common malignancy in women worldwide. Despite treatment, recurrence and metastasis are common. Lobular breast cancer most commonly metastasizes to the lungs, liver, lymph nodes, and sites in the brain. Metastasis to the gastrointestinal tract is rare, with few cases reported to date.

CASE REPORT: This report describes a patient with late colon and gastric metastases from lobular breast cancer mimicking primary colon and gastric cancers.

CONCLUSIONS: Immunohistochemical methods can help differentiate metastatic breast disease to the gastrointestinal tract from primary gastrointestinal malignancy.

Keywords: Breast Neoplasms, Colonic Neoplasms, Biomarkers, Tumor, Carcinoma, Lobular, Diagnosis, Differential, Fatal Outcome, Gastrointestinal Neoplasms, Immunohistochemistry