cherry blossom disease

hi my mother in laws cherry blossom tree leaves are turning brown and dropping off on closer inspection i noticed some amber coloured jelly like goop coming out of a branch quite a bit of it to be honest about the size of a tomato. the tree is about 15 years old and has always been healthy.

i would like to know if it is a disease and what is it also how could i help the poor thing.

many thanks  

Sounds like bacterial canker - it'll need some pruning out followed by spraying with Bordeaux mixture. Full description and instructions here.

Cherry trees are prone to Honey Fungus as well.