Gallbladder and gastric metastasis as initial presentation of an undiagnosed primary lobular breast carcinoma

The most common sites for breast cancer metastases include the bones, lungs, liver, and brain. Metastases in the GI tract are rare and predominantly originate from lobular breast cancer. Gastric involvement by invasive lobular carcinoma (ILC) is rare and can mimic primary gastric malignancies, leading to diagnostic challenges. Metastasis of ILC to the gallbladder is exceedingly rare and often identified incidentally during cholecystectomy performed for presumed benign conditions. We present a case of a 62-year-old female patient with symptoms of weight loss and dysphagia. After CT and gastroscopy, gastrectomy and cholecystectomy were performed due to suspicion of gastric carcinoma. Histology and immunohistochemical profiling, with estrogen receptor (ER), progesterone receptor (PR), E-cadherin, GATA3, Mammaglobin, and GCDFP-15, favored the diagnosis of lobular breast carcinoma metastasis over primary gastric adenocarcinoma. Awareness of these atypical presentations is crucial for accurate diagnosis and effective management, as misdiagnosis can result in suboptimal treatment strategies.