I thought of several things -
A large fluke ova filled with redia - see Fasciola gigantium
A macrophage or large epithelial filled with ingested or invading organisms
Hydatiform cyst - Echinococcus does form cysts in the avoelar spaces (small air tubes in the lungs)and one of the drugs used is the one you are using.
see: (search words - human lung parasites)
List of parasites
of humans - Wikipedia, the free encyclopedia
lungs, small intestine, blood: stool: common in tropical, warm, moist climates ... External links. A List of Human Intestinal parasites
accessed May 2008
go down to Echinococcus in the chart and follow the link to the Wikipedia article on Echinococcus.