So a lump has gradually been growing on the right side of Mr. Bleu, my betta. It's behind his eye, just above his little swimming fins. He seems to be acting normal (ie. eats like a pig, builds bubble nests) and aside from the fin rot I've battled on and off, is fine. He is quite old though, at least 2 years now and I'm afraid the lump might be cancer. What are your opinions of this?