I've never seen that sort of thing on raspberries but It looks like it could be an insect.
I had a whole bunch or pretty extreme growths late last season with what I'm nearly sure was a gall wasp. I cut open the growths and there were a bunch of larva living in there. If your plant is vigorous, which it looks like, you might want to go ahead a lop it off and take a look inside the growth. It would sure give the good folks here more information to work with.