Help, Does My Fish Have Cancer?

Hello all, my sons fish has run into trouble and we are unable to diagnose his problem. Please help us figure out what it may be.
The fish has normal energy, eats a ton, and other than the bulge that is created against his spine he swims perfectly.
The bulge started about 10 days ago and has been getting progressively worse. At first I thought he had been attached by the newt but these past few days have shown otherwise. The bulges appear to be dark purple, i think it may be blood. The bulges are centralized to the left side of his body directly where the fin and tail meet (where the first bulge started) and run the entire height of his body (top to bottom).
Not sure what to look for so any advice would be great. I have google searched the heck out of this and seem to be hitting a wall.

Thanks all,

Joe

Tumors shouldn't grow that quickly. I would think it to be either a viral or bacterial infection. The best thing would be to put the fish in a 10 gallon hospital tank and add salt and treat with a wide spectrum antibiotic.

Agree, just by looking at the pictures, I feel very bad for the fish. A hospital tank would greatly benefit him and will increase his survival.