How To Treat This Lesion/Ulcer On My Goldfish?

I am attaching a photo of a goldfish that I found with the same problem mine has -- note the large white lesion near the fin. My goldfish has had this for a short while but it seems to be getting larger in the past week. He does not appear to be sick, but I am concerned that it is growing.

What is it?

How should I treat it?

I am not able to find an answer on all the sites on the internet that I have searched.

Thanks, Pam

Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Ulcers are pink or red with a circling of dead white tissue around the edges.

The white lesion does it look fluffy like cotton wool.

Where the pic.

Does the growth look like a cauliflower.

Actually -- descibing it as a cauliflower is a good one!! It's white/cream colored, and is sort of lumpy like a cauliflower (definitely not smooth)!!

The fish seems fine but I am concerned that I should be treating this if it is growing.

Pam

Lymphocystis



Symptoms:

Fish infected with Lymphocystis will present with clusters of whitish, berry-like growths on the skin and fins. These "clusters" may resemble small clutches of eggs or cauliflower (hence, it is sometimes called Cauliflower Disease). They will be clearly visible and may even become extremely large. This disease often affects the fins first.



Cause:

Viral infection. The virus will eventually kill the fish if it is unable to mount a strong enough immune response as the virus rampages through the fish’s tissues, destroying its cells.



Treatment:

As with all viral infections, there is no suitable cure or efficacious treatment; however Quick Cure claims to be helpful. I have also heard of people who trim the fish's fins, followed by several baths in Malachite Green. Fortunately, this disease is uncommon and in some cases, infected fish are able to recover quickly without treatment.

Lymphocystis is highly infectious. When infected cells from the fish’s skin or fins burst the virus is spread throughout the aquarium and can remain contagious for periods of up to two months. Fish not showing symptoms should be removed from the aquarium and placed in quarantine, away from other fish, for at least 60 days. Note, remove uninfected fish, not the other way around because the aquarium has become contaminated. The infected aquarium should be emptied and thoroughly disinfected before returning any fish to it. Do not use soap to clean the aquarium.

Thanks!! Pam

Poor thing.
Does it sound like lymthocystis that the fish has to you.