Bladder metastasis from lung adenocarcinoma: a difficult differential diagnosis with primary bladder adenocarcinoma

BACKGROUND Bladder metastases from lung adenocarcinoma are extremely rare; in the seven previously reported cases, the finding of an intact epithelium overlying the bladder tumour was considered suggestive of a secondary lesion. We describe the first case of bladder metastasis from lung adenocarcinoma whereby endoscopic appearance was strongly consistent with primary bladder cancer, thus complicating the differential diagnosis with primary bladder adenocarcinoma. CASE REPORT A 65-year-old woman with a 13-year history of clean intermittent catheterization was diagnosed with a right lung adenocarcinoma metastatic to mediastinal and right supraclavicular nodes, as well as to the left lung, and treated with six cycles of cisplatin/pemetrexed, followed by six cycles of pemetrexed only. The 18-month follow-up computed tomography revealed several solid lesions of the bladder wall and she was scheduled for transurethral resection of bladder tumours. Endoscopic appearance was strongly consistent with primary bladder cancer but a thorough pathologic evaluation allowed the diagnosis of bladder metastasis from lung adenocarcinoma. CONCLUSIONS Differentiating primary bladder adenocarcinoma from metastatic adenocarcinoma lesions can be difficult. An endoscopic appearance consistent with primary bladder cancer further complicates the differential diagnosis, which heavily relies on pathologic evaluation and specific immunohistochemical staining.