BREAST CANCER METASTASIS TO COLON

Objectives: The most frequent sites of breast cancer metastasis are local and distant lymph nodes, lungs, brain, liver and bone. Triple-negative breast carcinoma with metastasis to the gastrointestinal (GI) tract is a rare occurrence, with the more common sites of metastasis being the fundus and antrum of the stomach. Colorectal breast cancer metastasis is less common and can often mimic large bowel cancer, causing a misdiagnosis of primary intestinal cancer. Most GI tract metastases are seen from invasive lobular carcinomas, rather than invasive ductal carcinoma. This report describes a case of symptomatic lower GI bleeding caused by an invasive ductal breast carcinoma metastasis to the colon.

A 67-year-old female with a past medical history of triple-negative metastatic breast carcinoma and T4N0M0 left lung adenocarcinoma presented to the emergency department (ED) with large volume melena. In the ED, the patient reported recent increase in watery bowel movements prior to this bloody bowel movement. Imaging showed a necrotic mass arising from the transverse colon that had increased in size compared to a CT scan several months prior. She also had extensive metastatic disease throughout the mesentery, adrenal glands, retroperitoneum, and subcutaneous tissues. Gastroenterology was consulted and performed a colonoscopy, revealing an infiltrative non-obstructing colonic mass. The mass was biopsied, and pathology showed adenocarcinoma consistent with triple-negative metastatic mammary carcinoma. After multiple blood transfusions and attempts at non-operative management, surgical consultation was obtained, and she was offered palliative resection. During the operation, a large mass in the distal transverse colon and adjacent mesentery was identified. The mass was found to be adherent to the small intestine and stomach, requiring en bloc segmental colectomy, small bowel resection and gastric wedge resection. The patient recovered well from her surgery and her hematochezia resolved. She remains on palliative treatment for her multiple remaining metastases.

Gastrointestinal metastasis of breast cancer can be asymptomatic or symptomatic, presenting with nausea, abdominal pain, bowel obstruction, dysphagia, or GI bleed. Treatment is typically palliative in nature and may include placement of endoluminal stents, endovascular or endoscopic therapy, or surgical resection. Intestinal involvement of metastatic breast cancer suggests more widespread metastatic disease and warrants systemic treatment. Even with treatment, remissions are common with about 32-53% of patients presenting with recurrent GI tract metastasis after 5 years. In patients with a history of breast cancer who present with new colonic gastrointestinal mass or onset of GI symptoms, metastatic breast cancer should be considered.

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