cysts

what does it mean when a cyst is found on the liver after living with hepc for 20 odd years and can a cyst of 7mm be dangerous.

[HCA]

All you ever wanted to know about liver cysts here;
http://www.britishlivertrust.org.uk/home/the-liver/liver-diseases/cystic-disease.aspx
I quickly scanned this article and didn't notice anything alarming.

[Andromedae]

I'm not sure if this is relevant but when I had an ultrasound done they found several "spots" one of which was about 1 cm in diameter and several smaller dots..  A follow up MRI confirmed that they were all something called "hemangiomas"  which are just an intense collection of blood vessels.  I don't know if your "cyst" is actually something like that (with perhaps a confusion in terminology somewhere) or if it is something else.  Not all "spots" found in ultrasound or MRI are dangerous.

HOWEVER, you asked if a cyst of 7mm can be dangerous.  The answer is that ANYTHING can be dangerous and only your doctor can tell you whether what you have is something to be concerned about or not.  You should get whatever follow up tests are necessary to confirm what you need to know.  We can all tell you our personal experiences here but no one here can know what is going on in your case.  Only your doctor and follow up tests can know for sure.