a hydatid cyst of a multiloculate type, usually in the liver, caused by Echinococcus multilocularis, adult forms of which are found in foxes; larvae (alveolar hydatid) are found chiefly in voles and lemmings, but also among humans such as trappers and others who handle pelts of infected foxes and other carnivores; growth is by exogenous budding and is not limited by an outer laminated membrane as in the hydatid cyst from E. granulosus; necrosis, cavitation, contiguous spread, and death usually ensue. SYN: multilocular hydatid cyst, multiloculate hydatid cyst.