Urinary bladder invasion secondary to dissemination of gallbladder cancer: an unusual presentation.

Gallbladder cancer is an aggressive malignancy that is often diagnosed at an advanced stage, with frequent metastatic spread. Urinary bladder invasion caused by disseminated gallbladder cancer is extremely rare. A 56-year-old man presented with gross hematuria. Imaging revealed tumors in the gallbladder and urinary bladder with peritoneal dissemination. Transurethral resection of the urinary bladder tumor showed adenocarcinoma. Immunohistochemical analysis demonstrated positivity for CK7 and CDX2 and negativity for CK20, findings inconsistent with urachal carcinoma. Biopsy specimens from the gallbladder tumor and bile duct stricture revealed poorly differentiated adenocarcinoma with an identical immunohistochemical profile, leading to a diagnosis of urinary bladder involvement from gallbladder cancer. Despite systemic chemotherapy, the patient died 10 months after treatment initiation. Pathological autopsy confirmed urinary bladder invasion caused by peritoneal dissemination. This case illustrates a rare presentation of gallbladder cancer with urinary bladder invasion causing hematuria and highlights the importance of considering disseminated disease when evaluating urinary bladder tumors in patients with gallbladder cancer.