Background: Although breast cancer (BC) is the most common malignancy in women, metastatic involvement of upper gastrointestinal (UGI) tract is uncommon. UGI metastases may affect quality of life and overall survival, but presenting with nonspecific symptoms, diagnosis may be delayed.

Case Presentation: We describe the case of a 70-year-old woman with a history of invasive lobular breast carcinoma diagnosed in 2013 and treated with left mastectomy and axillary dissection. Despite adjuvant chemotherapy, in 2020 bones metastasis were diagnosed. Chemotherapeutic agents were administered during the years with stability of the bones metastasis and no other organ involvement at the follow-up CT scans. In August 2025 she underwent EGD for progressive dyspepsia, vomiting, and weight loss. Endoscopy revealed a gastric mucosa with granular-aspect, congestion, edema, redness and multiple confluent fibrotic ulcers of 1 to 2 cm. Moreover, multiple duodenal polypoid lesions, ranging from 3 to 10 mm, with central depression and non-adenomatous pattern at digital chromoendoscopy were identified. Biopsies were performed on gastric ulcers and polypoid lesions. Histopathology demonstrated localization of lobular breast carcinoma, with immunohistochemical expression of GATA3 and lack of E-cadherin, CDX2 and the receptors for estrogen, progesterone, and HER2 proteins. According to the metastatic involvement of UGI tract, supportive palliative care was proposed. The patient was still alive 3 month after endoscopy.

Conclusion: UGI metastasis from breast carcinoma are rare, but they should be considered in patients with history of BC presenting with persistent UGI symptoms. Early recognition is crucial for the appropriate oncological management.