Gastric metastasis from breast carcinoma is rare and poses a substantial diagnostic difficulty since it closely mimics primary diffuse-type gastric adenocarcinoma on histo-morphology. We report a 43-year-old premenopausal woman who presented with dysphagia, loss of appetite, loss of weight, melaena, and anaemia. Oesophago-gastroduodenal endoscopy revealed an ulcerated gastric lesion involving both greater and lesser curvatures, and biopsy showed poorly cohesive adenocarcinoma. Cross-sectional imaging demonstrated diffuse gastric wall thickening with bilateral ovarian masses, nodal deposits, peritoneal disease, bilateral multiple breast lesions, axillary lymph nodes and widespread skeletal metastases, a pattern strongly suggestive of advanced gastric malignancy, leading to an initial diagnosis of primary gastric cancer. She was commenced on FLOT (Fluorouracil, Leucovorin, Oxaliplatin, and Docetaxel) chemotherapy. Subsequent biopsy of a right breast lesion revealed oestrogen and progesterone receptor– positive, HER2-negative invasive lobular carcinoma. Further immunohistochemical studies confirmed the gastric lesion to be metastatic than a gastric primary. The diagnosis was revised to metastatic breast carcinoma, and treatment was changed to CDK4/6 inhibitor in combination with an aromatase inhibitor, resulting in significant clinical improvement. This case highlights the importance of a high index of suspicion of primary breast cancer in a female when imaging favors metastatic deposits along with clinicopathological and immunohistochemical correlation in evaluating poorly differentiated likely metastatic gastric carcinoma with deposits in the breast.
Keywords: Gastric metastasis; Immunohistochemistry; Metastatic Breast Carcinoma.
Citation: Nadarajah, S. et al., (2026). When Breast Cancer Masquerades as Gastric Cancer : Gastric Metastasis from Invasive Lobular Carcinoma. J Medical Case Repo 8(2):1-4.
DOI : https://doi.org/10.47485/2767-5416.1149