Acer Fungus

Morning!
A newby here so apologies if this is in the wrong place or similar.
I have just discovered a lot of fungus growth on one main branch of our Acer. Photo attached. From what I’ve read elsewhere I’m guessing it cannot be treated but needs cutting out completely? Hopefully not killing the tree.
Thoughts and advice please.

 

The branch is dead cut it out, I am more curios why its died is the rest of the tree healthy ?

 

Thanks for responding so quickly Perki. I’ve no idea why it died at all, it was fine in the summer. I’ll cut it out and prune the remainder. Thanks again

 

I'd have thought that that particular branch had been dead for a year or so, looking at it.
There are a couple of snags on it which could have caused it to die back , after which the fungus could have got in.