sick goldfish...does anyone know what this is?

this is not the 1st one that this fish has had...he has had 3 in the past month...they come n then heal...it sticks out
 
Sorry, only just caught up with this.
Its deffinitely Lymphocystis and as its a virus theres no cure. The lumps as youve said come and go and all you can do is keep him isolated as its contagious. A vet can remove them if they grow over the eye or gills. Ive seen them cover a big area and in time they will grow internally into organs and that may be fatal.
Ive seen fish live with these lumps for years and indeed one fish I know has had then for over 6 years and is now 12 years old, so dont give up on him. Its just unsightly.
 
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