Long-term survival of a patient with extensive small cell carcinoma of unknown primary etiology complicated by nephrotic syndrome.

We experienced a case of nephrotic syndrome (membranous nephropathy) complicated by extensive small cell carcinoma of unknown primary etiology that was diagnosed based on the findings of bilateral cervical and mediastinal lymphadenopathy. A complete cancer response and proteinuria remission following radical chemoradiation therapy were documented. The status of a complete response and nephrosis remission persisted for more than three years. This is the first report to demonstrate the long-term survival of a patient with extensive small cell carcinoma of unknown primary etiology complicated by paraneoplastic nephrotic syndrome.