Inactive renin: a tumor marker in nephroblastoma.

Renin-containing cells have been identified in nephroblastoma. A prospective study of eight children with nephroblastoma has demonstrated abnormally high levels of total renin. The increase in total renin was due to increased levels of inactive renin (prorenin), rather than the active renin. These high levels decreased to normal after operation. The plasma level of inactive renin could be a useful biochemical tumor marker in nephroblastoma.