Rare Breast Metastasis From Urothelial Carcinoma: A Case Report and Literature Review.

Bladder cancer is a prevalent malignancy globally, significantly affecting patient quality of life, morbidity, mortality, and healthcare costs. Disparities in bladder cancer incidence and mortality rates among countries result from varying risk factors, detection methods, and diagnostic techniques. Enhanced imaging has led to more precise staging, while advancements in surgical techniques have been paired with superior chemotherapy protocols. Bladder cancer frequently metastasises to the lymph nodes, bone, liver, lung, and peritoneum, but rarely to the breast. Metastases to the breast originating from bladder cancer present difficulties in identification and require standard invasive techniques. We report a case of a 79-year-old female diagnosed with a muscle-invasive bladder tumour who underwent a positron emission tomography-computed tomography (PET-CT) scan that demonstrated significant localised activity within the right breast. An ultrasound scan and mammography of the right breast revealed a 10 mm ill-defined mass in the upper outer quadrant and two minor ill-defined masses measuring 6mm and 10mm in the upper inner quadrant, with no concomitant axillary lymphadenopathy. A core cut biopsy and immunohistochemistry of the prior lesions were performed, which are morphologically and immunophenotypically similar, supporting a diagnosis of metastatic urothelial carcinoma.