Unique Presentation of Gastric Outlet Obstruction Due to Breast Cancer Metastasis: A Case Report

Invasive lobular carcinoma (ILC), a subtype of breast cancer, is challenging to detect early due to its diffuse spread, and metastasis often occurs before diagnosis. While ILC commonly metastasizes to the bone and gastrointestinal (GI) tract, gastric involvement, particularly causing gastric outlet obstruction (GOO), is rare. We present a 63-year-old Southeast Asian woman with a history of left breast ILC, who developed GOO. Diagnostic evaluations, including endoscopy and PET CT, revealed a large invasive mass in the gastric antrum, confirmed as metastatic breast cancer. A stent was placed to relieve the obstruction, and the patient started chemotherapy. This case highlights the unusual presentation of ILC metastasizing to the stomach, forming a fungating mass, which deviates from the typical linitis plastica pattern. It underscores the importance of recognizing atypical metastatic behaviors in ILC and the need for further research to improve diagnostic approaches in such rare cases.