Small-Intestinal Metastasis from Breast Cancer Presenting with Gastrointestinal Bleeding: A Case Report.

[INTRODUCTION] Gastrointestinal metastases from breast cancer are rare, especially in the small intestine, and diagnosis is often difficult due to nonspecific symptoms and limited detectability with standard endoscopy. Intestinal bleeding, although uncommon, may become clinically significant. We report a case of recurrent triple-negative breast cancer in which persistent anemia during sacituzumab govitecan (SG) therapy was attributed to small-bowel metastasis, and small-bowel evaluation using capsule endoscopy and balloon-assisted enteroscopy led to the diagnosis after standard upper and lower endoscopy failed to identify the source of bleeding.

[CASE PRESENTATION] A 50-year-old woman with recurrent triple-negative breast cancer underwent multiple systemic treatments before receiving sacituzumab govitecan. From treatment initiation, grade 3 anemia persisted despite transfusion support. Blood test findings indicated ongoing blood loss, including normocytic features with preserved marrow activity. Positive fecal occult blood prompted capsule endoscopy and balloon-assisted enteroscopy, which revealed a protruding jejunal lesion with active bleeding. Biopsy confirmed metastatic breast cancer. Because endoscopic hemostasis was difficult to achieve, laparoscopic partial small-bowel resection was subsequently performed. Histopathology of the resected specimen demonstrated multiple transmural lesions, many of which were suggestive of nodal metastases. Postoperatively, anemia resolved without transfusion, and SG therapy was successfully resumed after surgery.

[CONCLUSIONS] Small-intestinal metastasis causing bleeding is difficult to diagnose due to its nonspecific clinical presentation, and dedicated small-bowel evaluation is essential when standard endoscopy fails to identify the bleeding source.