Invasive ductal breast cancer metastatic to the sigmoid colon

The most common sites of breast cancer metastasis are the bone, lung, liver and brain. However, colonic metastases from breast cancer are very rare in the clinic. We describe an unusual case of sigmoid colonic metastasis from invasive ductal breast cancer. With this report, we should increase the clinical awareness that any patient with a colorectal lesion and a history of malignancy should be considered to have a metastasis until proven otherwise. Early diagnosis is very important, which enables prompt initiation of systemic treatment, such as chemotherapy, endocrine therapy or both, thus avoiding unnecessary radical surgical resection and improving the prognosis.