My goldfish has a lump ;o(

Question
HI, I'm hoping you may have some idea - a few months ago my goldfish developed a lump on his side - i tried various treatments to try and treat the lump but to no avail (tried bacterial control, methylene blue, fungus/ulcer treatments - just incase it was a form of this...The lump initially was just a small lump under the scales - the scales did not raise or there was no open wound.... the lump is now massive, it doesn't look like there are scales on it now, its just a mass lump it did look like a chunk had been taken out of it but doesn't seem to cause the fish any distress and the chunk taken out has now appeared to of filled back in - the fish seems happy and healthy and still has a great appetite... i have noticed tho that another fish seems to have a small lump on his head but again is growing, the 2fish were from the same shop about a year/2years ago so i don't know if there was something wrong with the batch - any ideas as to what the lumps maybe and any cure for getting rid of it? when i've looked online - the prognosis doesn't look good-most sites look give the impression its cancerous... :o(
Your help/advise would be appreciated.
Many thanks in advance,
Tee
P.s - do you know anything about koi carp? if so, one of my koi fish doesn't appear to be able to open his mouth and had not fed for a few months now - he looks healthy but obviously not a good sign that he is not feeding - any idea as to why he does not appear to be able to open his mouth? The other koi in the pond are fine and feeding well and they have no probs opening their mouths, either out the water or extending it under the water - but Ben doesn't do either at all - very worried, especially as he is about 2ft long and is my favorite!! your help again or any advice you can give is much appreciated... Many thanks and take care.

Answer
Hi Tee:  I would suspect that the lump may actually be a tumor.  I suspect a tumor because the issue has been going on for a while without much development in terms of open soars, etc.  It may be an internal parasite... but if the second goldfish is developing a lump on its head I again lean toward a tumor.  Mass breeding of goldfish and other tropical fish tend to result in tumors.   If the fish are functioning and do not seem to be impeded by the growth then I would just keep an eye on them.  If they develop further and especially if they develop into sores then please let me know and I can suggest treatment for those.  As for KOI... I am not an expert on KOI.  I have heard that sometimes their mouth will grow closed and sometimes a mobile vet can help with opening it back up again. Apparently their lips or the tissue inside of their mouth will grow together.  I would have a mobile vet check him/her out.  dave