Gastrointestinal metastasis secondary to invasive lobular carcinoma of the breast: A case report

BACKGROUND Gastrointestinal metastasis of breast cancer is rare, and clinicians may not have previously encountered this disease in clinical practice. CASE SUMMARY We report a patient with invasive lobular carcinoma of the breast who developed gastrointestinal metastasis two years after modified radical surgery. Mild elevation of carbohydrate antigen 15-3 was observed in the patient at an early stage; however, diagnosis and treatment were delayed due to non-specific clinical manifestations and no identifiable metastasis observed on imaging. CONCLUSION Clinicians should pay attention to gastrointestinal metastasis of breast cancer, especially invasive lobular carcinoma of the breast.