I had a cyst during the first 12 weeks of my pregnancy, the docs just monitored the growth of it via ultrasounds.  A co-worker of mine had one that was discovered around week 25, and she had a surgery to remove after her baby was born.  Cysts are a very common part of the woman system, the only reason to ever get concerned is if it get's larger then 4 cm.  Then rupture and flipping are possible.  If your doc isn't worried, I woudn't be either.  If your still worried talk to your doc.  With mine I was on bed rest for 4 days, and not allowed to do any heavy lifting, by week 15 it was gone.