There is no known cure for Lymphocytis. Cutting or removing the cysts is a risky procedure leaving an open wound exposed to a wide host of bacterias or worst still leaving behind some of the cyst to allow them to grow again.
Lymphocystis, once acquired, must run its course. There are some ways to decrease the chance of fish getting the disease
-Handle fish carefully to reduce injury to skin and fins and slime coat.
-Reduce or prevent stress on the fish. e.g AvoidStress overcrowding, starvation, overfeeding, sudden environmental changes
The disease usually runs its course in 4 or more weeks and then the enlarged cells rupture or slough off and release the viral particles into the water.
After lymphocystis lesions are lost, the host tissue will usually heal up rather quickly.
I have worked with many fishes of various species and do not recall a single death being directly due to a lymphocystis infection.
Hope this helps put some minds at ease.