Breast cancer metastasis to gallbladder and urinary bladder: A rare case report

Breast cancer is among the most frequently diagnosed malignancies worldwide, with metastases significantly impacting prognosis and treatment strategies. While the bones, lungs, liver, and brain are common metastatic sites, the involvement of the gallbladder and urinary bladder is exceedingly rare. These atypical metastatic sites pose considerable diagnostic challenges, often mimicking primary malignancies or benign conditions, thereby complicating timely diagnosis and appropriate management. We present the case of a 59-year-old female with a history of invasive lobular carcinoma of the right breast, diagnosed in 2018. Following a modified radical mastectomy, she underwent adjuvant chemotherapy, radiotherapy, and hormonal therapy, achieving an initial disease-free period. In June 2021, she presented with persistent vomiting, epigastric pain, and hematuria. Further evaluation revealed gastric outlet obstruction, prompting an exploratory laparotomy revealed a thickened gallbladder and pyloric narrowing. She underwent gastrojejunostomy (bypass surgery) with cholecystectomy, which confirmed metastatic carcinoma of lobular breast cancer origin in the gallbladder. Additional metastatic workup identified metastases to the bone and urinary bladder. Immunohistochemical analysis of metastatic lesions demonstrated estrogen receptor positivity, progesterone receptor positivity, and human epidermal growth factor receptor-2 negativity, consistent with the primary breast malignancy. Given her deteriorating condition, she commenced palliative chemotherapy with paclitaxel and zoledronic acid, subsequently transitioning to anastrozole and zoledronic acid. This case underscores the importance of recognizing rare metastatic patterns in breast cancer. Comprehensive diagnostic evaluation, integrating imaging, histopathology, and molecular profiling, is crucial for accurate diagnosis and appropriate treatment. Further research is necessary to elucidate the mechanisms driving metastasis to uncommon sites and improve therapeutic approaches. • A 59-year-old female with a history of invasive lobular carcinoma of the breast presented with recurrent vomiting, epigastric pain, and hematuria. • Imaging revealed metastatic spread to the urinary bladder and gallbladder. • Urinary bladder cystoscopy and biopsy confirmed invasive carcinoma consistent with metastatic breast cancer. • Immunohistochemistry findings remained consistent with the primary tumor (ER+/PR+/HER2-). • The patient received palliative chemotherapy with paclitaxel and zoledronic acid, later transitioning to anastrozole. • This case highlights the rare occurrence of urinary bladder metastases from lobular breast carcinoma and the importance of thorough metastatic evaluation.