At Significantly Higher Risk 
• This tumor is twice as frequent in men as in women, occurring mostly between the ages of 30 and 70.
• Those who smoke tobacco. 
• Patients on long-term dialysis with acquired polycystic kidneys have an increased risk, as do those with the
  inherited disease von Hippel-Lindau syndrome.
• Other (but weak) risk factors include obesity in women and a high animal-fat diet, both of which suggest a
  hormonal imbalance.
• A new finding is the frequent abnormality in the chromosome 3 genes, particularly in familial renal cancers.
  Both genes are needed to suppress tumor formation, and absence of one gene permits tumor growth. Such
  findings have led to trials of gene insertion therapy.