The Collaborative International Dictionary of English v.0.48:

Encysted \En*cyst"ed\, a.
   Inclosed in a cyst, or a sac, bladder, or vesicle; as, an
   encysted tumor.
   [1913 Webster]

         The encysted venom, or poison bag, beneath the adder's
         fang.                                    --Coleridge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

encysted
    adj 1: enclosed in (or as if in) a cyst