Unusual presentation of metastatic breast cancer to the bladder.

Breast adenocarcinoma is the most common cancer diagnosed in females in the United States, with 300,000 new cases and approximately 43,700 deaths expected in 2023. While breast cancer metastasis most commonly involves the bone, lungs, liver, and brain, it also has been shown to metastasize to the urinary tract. In this case study, we present a patient with a history of metastatic breast cancer who presented with the complaint of intermittent flank pain in the setting of left hydronephrosis. Diagnostic evaluation revealed a small bladder mass with subsequent resection and pathologic analysis reporting infiltrating carcinoma consistent with metastatic breast cancer.