An interesting unanswered question is why mutation of TSC1 or TSC2 in humans predominantly causes the development of renal AMLs, renal cysts and more rarely of renal carcinomas, whereas Tsc1 or Tsc2 mutation in rats or mice causes renal cysts, adenomas and carcinomas, but does not lead to the formation of renal AMLs21. This evidence concerns the gene TSC2 and cystic kidney disease.