Agaricus blazei is a medicinal mushroom that has an impressive record as an anti-cancer agent. The mushroom appears to be more effective at fighting cancer than cordyceps or mitaake.
Part the anti-cancer effect may be due to the mushroom's modulating effect on a type of immune cells called T-cells. T-cells can mature to become Th1 or Th2 cells--we know that some people develop a "skewing" towards overproduction of Th2 cells. This results in immune system "dysregulation" and increases in autoimminue diseases and certain cancers (read more about Th1/Th2 balance in my article on Immune Dysfunction). Research has shown that supplementing with Agaricus blazei corrects this "skewing" and normalizes immune function (read the evidence here).
There is an excellent Agaricus Extract available from www.immunesystemsgo.com (I have no finacial relationship with this product--I only recommend it because it's excellent!)