Urinary bladder metastasis from primary breast cancer, a rare and challenging diagnosis. A case report and literature review.

Introduction: and Importance: Liver, lung, bone and brain are usual sites for breast cancer metastases. However, colorectal, prostate and cervical tumors may directly invade the urinary bladder (UB), but hematogenous spread from distant organs like the breast, is extremely rare and may indicate poor prognosis. Case presentation: Here we describe the case of a 78-year-old female patient who was diagnosed with de novo metastatic breast cancer; initially to the bone and pleura with effusion, and then to the brain. Five years after her initial diagnosis, she presented with urinary symptoms and bilateral hydronephrosis. Work up showed diffuse thickening of the UB with no invasion from nearby structures; biopsy confirmed metastatic carcinoma of breast origin. Clinical discussion: Adenocarcinoma of the UB is uncommon. Distinguishing primary adenocarcinoma of the UB from secondary involvement is often challenging. When encountered, involvement by a secondary tumor, either by direct extension or distant metastasis, should be considered. Immunohistochemical stains are essential in reaching an accurate diagnosis. Conclusions: Breast cancer rarely metastasizes to the urinary bladder and prognosis is usually poor. Detailed medical history, imaging, and immunohistochemical studies on biopsy specimen should help reach accurate diagnosis.