[Localized sarcomatoid renal carcinoma. Which factors may predict its course?]

Sarcomatoid renal carcinoma constitutes an uncommon variant of renal carcinoma. Typically its behaviour is more aggressive than other forms of renal carcinoma and usually it is diagnosed at advanced stages. The main prognostic factor is the clinical stage at the time of the diagnosis. However, some cases initially are diagnosed at low stages having a poor prognosis, probably because there are other factors than the clinical stage which determinate its outcome. We report a case of sarcomatoid renal carcinoma confined inside the kidney capsule at the time of the diagnosis which had a rapidly bad progression. We review the characteristics of this tumour variant and analyse what factors, basically histological, could be helpful to predict its evolution.