A rare case of synchronous breast cancer metastasis to colonic and gastric mucosa-case report and review of literature.

Distant metastasis from primary breast cancer typically affects the brain, liver, lungs, and bones. Less than 1% of patients exhibit metastasis to the stomach or colon, mimicking primary gastrointestinal tumors upon initial presentation. Here, we present the case of a middle-aged female who initially presented with synchronous breast cancer and metastasis to the gastrointestinal tract. A middle-aged female presented to our center with GI symptoms. Prior upper GI endoscopy showed diffuse infiltration of atypical tumor cells resembling poorly cohesive adenocarcinoma of the stomach. Immunohistochemical stains were positive for markers indicative of breast origin, and negative for CDX2 and TTF1, ruling out gastrointestinal and lung origins, respectively. Breast ultrasound confirmed architectural disruption, and suspicious bilateral axillary lymph nodes. Biopsy of the axillary lymph nodes confirmed the presence of breast cancer cells. She was treated with Letrozole and Ribociclib showing complete resolution on subsequent CT scans. The patient continues this regimen and is now in clinical and radiological remission for the past four years.