Diagnostic challenges in a rare case of bladder metastasis from lung hepatoid adenocarcinoma: The first reported case

Secondary bladder tumors are rare, and hematogenous bladder metastases from lung cancer are exceptionally uncommon. We report the first documented case of bladder metastasis from pulmonary hepatoid adenocarcinoma (HAC) in a 72-year-old man undergoing treatment for lung cancer. An asymptomatic bladder mass was detected during follow-up. Histopathology and immunohistochemistry confirmed metastatic pulmonary HAC and excluded primary urothelial and hepatic tumors. This case highlights the diagnostic value of comprehensive immunohistochemistry and clinicoradiological correlation in distinguishing secondary bladder tumors. Early recognition is essential to guide appropriate multidisciplinary management, although prognosis remains poor.