Unusual Gastric Metastasis in Triple-Negative (Estrogen Receptor/Progesterone Receptor/HER2neu Negative) GATA-Binding Protein 3-Positive Breast Cancer.

Triple-negative breast cancer (TNBC) accounts for 20%-25% of breast cancer cases. Around 10%-15% of patients with breast cancer present with upfront metastasis. Lymph node, bone, and liver are common sites of metastasis in hormone-positive breast cancer while brain, lungs, and liver in TNBC. Although visceral metastasis is common in TNBC, metastasis to stomach is unusual. Morphological similarity of primary gastric carcinoma and lobular invasive breast carcinoma often leads to misdiagnosis. Meticulous review of histopathology and immunohistochemistry is essential for diagnosis. We present a case of carcinoma breast with unusual gastric nodular metastasis detected on F-fluorodeoxyglucose positron emission tomography-computed tomography.