Comet with growth

[SkinnyChicken]

I recently inherited a pond at my new house that is home to 7 Goldfish, Shebumpkins and Comets. Not long after I moved in I noticed that one of the comets has a rather large growth on its side. Unfortunately, due to the location of the pond and lack of direct sunlight I can't seem to get any clear photographs of the lump. Nor do I know how old the fish is - though he is perhaps 6/7 inches long. None of the other fish have any similar growth and all seem very healthy.

I took him out of the pond into a tank and have been treating with salt and a broad spectrum antifungal medication for a couple of weeks now.

The fish in question is otherwise happy and healthy and doesn't seem to show any effects at having the growth - not when he was still in the pond, and not now that he's been medicated for just over two weeks.

The growth, however, has not gone down even slightly and this has led me to think that maybe the growth itself may have stopped growing (i.e. the infection has cleared itself up over time). And the growth is therefore now a permanent lump (rather than growth that implies that it is still growing) and will not disappear no matter what I throw at it.

I'm sorry I have no photograph of the fish and realise that any advice is given blindly, but still, I'd appreciate any advice you might offer.

Cheers

[Mvjnz]

It could be a tumour, seeing as it's not responding to medication.