Breast metastasis of signet ring cell carcinoma from the colon: a case report

BACKGROUND: Colon cancer is one of the most common diagnosed malignancies. Despite the use of surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy, and other comprehensive treatments, distant metastasis is still one of the main causes for dying of colon cancer. The common metastatic site of colon cancer is the liver, lung, and bone. In this article, we report a rare case of breast metastasis of signet ring cell carcinoma from the colon. CASE PRESENTATION: A 44-year-old woman was diagnosed with colon cancer and received a radical surgery of colon cancer in 2019. Combined with postoperative pathological and computed tomography (CT) images, a diagnosis of cT3N2M0 mucinous adenocarcinoma of colon (according to AJCC cancer staging manual, Version 8) was established. Adjuvant chemotherapy (XELOX: oxaliplatin 130 mg/m(2) on day 1 plus capecitabine 1000 mg/m(2) twice daily on days 1 to 14 every 3 weeks for 18 weeks) was performed followed by surgical resection. Fourteen months later, the patient underwent mastectomy for breast mass, which was diagnosed pathologically as metastasis of signet ring cell carcinoma from the colon. XELOX chemotherapy regimen (oxaliplatin 130 mg/m(2) on day 1 plus capecitabine 1000 mg/m(2) twice daily on days 1 to 14 every 3 weeks for 24 weeks) combined with bevacizumab (7.5 mg/kg on day 1) was used after the mastectomy. The patient had stable disease according to her last examination (RECIST criteria). CONCLUSION: It is rare to find a report of a patient of colon cancer that metastasizes to breast. We hope to increase treatment experience for patients with this rare metastasis.