Interleukin-6-producing thymic squamous cell carcinoma associated with Castleman's disease and nephrotic syndrome.

When a 63-year-old man was hospitalized with nephrotic syndrome due to focal segmental glomerulosclerosis, a mediastinal mass was discovered. A biopsy specimen obtained by mediastinoscopy showed findings compatible with the plasma cell type of Castleman's disease. Fever, anemia, and anti-nuclear antibody were present.