Gastric Metastasis with Lobular Phenotype from a Primary Invasive Ductal Breast Carcinoma: A Case Report.

Introduction: Breast cancer is a leading cause of cancer-related mortality in women, with common metastatic sites including bone, lung, liver, and brain. Metastasis to the gastrointestinal tract, particularly the stomach, is a rare occurrence, with a reported clinical incidence of 0.2-0.7%. Its nonspecific symptomatology and heterogeneous endoscopic presentation often lead to diagnostic confusion with primary gastric cancer or benign conditions. Case Presentation: We report the case of a 51-year-old woman with a history of stage IIIC invasive ductal breast cancer, treated 9 years prior with multimodal therapy. She presented with a 6-month history of severe abdominal pain, significant weight loss (15 kg), vomiting, and diarrhea, initially managed as a Conclusion: This case underscores that gastric metastasis should be considered in breast cancer survivors presenting with persistent upper GI symptoms, even many years after initial remission. It highlights the critical role of immunohistochemistry in achieving a correct diagnosis, which is essential for guiding appropriate systemic therapy and avoiding unnecessary surgical intervention. A multidisciplinary approach is paramount for managing this rare manifestation of advanced breast cancer.