Our flowering cherry tree has growths on the bottom of its leaves

Question

Flowering Cherry tree My dad showed me his flowering cherry tree in our backyard. He said it has been there for 30 or more years. It hasn't had any problems that we know about but it is fairly small. It was only about 2 weeks ago that some of the leaves started to have growths around it (mostly on the bottom) in clumps or spaced out. We let it be because we didn't know what it was and we thought the tree would get rid of it itself. But the growths haven't shown any signs of disappearing so I decided to try searching up cures on the Internet but I cant seem to find any. The tree doesn't seem to be dying, but the only way to remove the growths is to pull off the leaves from the tree which would kill the tree if we pulled off all the leaves with the growths. What is this disease? Is there a way to remove the growths without killing the tree? Can it spread to other plants in our backyard?

Answer
Joseph:
These are leaf galls caused by a very small Eriophyid mite (not a true insect- it has 8 legs!).  It is called a spindle gall and usually a cosmetic issue. Go to "Google Images" and take a look.  Rake up fallen leaves and destroy, since these critters can come back next year from these old galls. Be sure to just water your tree and fertilize to maintain good vigorous growth.
P.S. Thanks for the Photo!!
Steve