Help! Funny Lump, And I Think It's A Tumor!

I have a very beautiful albino halfmoon betta named Triton who I love very much. I got him in January from a Pet Smart, and at the time he seemed perfectly healthy and alive. But sometime in March, he started to grow a funny lump on the side of his head. I didn't worry much, and I waited to see if it would get better. Now the lump is almost big enough to look like a second head. Recently I moved him into a "hospital vase" to treat him for a little fin rot, and ever since the move he has been extremely weak and has stopped eating. The growth didn't seem to change his health at all, so I wasn't too worried, and I took my time to try and find out what it is. I've had suspicions that it's a tumor since I first noticed it, and the research I've done has made me fairly sure about it.
 
I have a picture of him, and I hope someone can confirm or deny my theory and help me treat whatever it is.
 

this might be helpful http/www.fishforums.net/index.php?/topic/441031-is-this-lymphocystis/

Thank you for this, I'll look into it and see if I can do anything. I was so excited that I found an albino betta, but when I discovered the lump, I felt slightly cheated. But I guess that's the way it goes when your only nearby pet stores are PetSmart and PetCo.