Unknown lump

[Bob V]

Can anyone identify the lump on my gold ram.  It's the right side near his tail. Started to notice the fish tilting to one side at times but remains active and is eating well.

He lives in a seasoned 30gal community tank. (About 2 years) pH 7.2 zero ammonia and nitrite. 40ppm nitrate, kh 120 gh ~100. Temp 78 degrees.

Planted tank with 10 neons, 4 platys 3cory and 5 amano shrimp. No new additions for last year.

Any ideas? Should I quarantine? Meds?

[GardenStateGoldfish]

how quickly did it grow? Did you notice any injury in the area before that? 

I don't know much about anything other then goldfish and snails, however I know fish can be prone to cysts or tumors. 

There is also some other forms of Pox and stuff also but not sure if they affect that type of fish.