You don't have to look closely for what he's talking about! I have seen these things as big around as nickels, and they can have a lot of puss in them.
It's disgusting, that's for sure. I, for one, am not eating puss from cysts in meat. I'm certainly not serving it to anyone. I did come up with a plan, though, as I certainly didn't want to throw a nice, red meat salmon away:
If you see the cysts or puss, go head and skin the filet. Next, cut the filet into small enough pieces so that you can see where there are or aren't any cysts. You will notice there is a kind of pattern as to where they are located along the back bone. Not all of them follow the pattern, though so be careful. When you locate them, carefully cut them out. If they rupture, do your best not to barf and wipe it clean with a paper towel, then cut the rest of it out. Keep cutting up the filet and inspecting as you go. If you have a large piece, cut it in half and make sure you got all of the cysts. You don't want any surprises.
Also, go ahead and remove your 'pin bone' layer at this time by either cutting the entire row out, or pulling them with pliers or tweezers. You should probably do that before you start to cut up the filet, come to think of it. There are videos on youtube that show you how to do it.
Now, cut the grey meat off of the back side of the filet. You now have prime, skinless, boneless, CYSTLESS salmon meat that you can do all kinds of thing with. My son's favorite is fried, fish n chips style. Fresh salmon burgers and salmon cakes are my favorite things to make with it. For those salmon cakes, simply find your favorite crab cake recipe and substitute your fresh salmon meat for the crab. mmmmmmm, so good!! Take your pre-made cakes and burgers, vacuum pack a meal's worth per bag and throw 'em in the freezer!
I hope that helps. If the cysts are so small and few that you can't cut them out, then maybe the guys in the other posts have the better advice, I just haven't encountered that, myself.
Ed
p.s. I hope this doesn't offend you, but there are also some videos that show how to filet a fish.