Echinococcosis (hydatid disease)

It is contracted by ingestion of Echinococcus granulosus or Echinococcus multilocularis cestode eggs, which hatch into embryos in the small intestine, enter the circulatory system and form hydatid cysts in many organs (such as the lung).

In cytologic specimens, the laminated hydatid cystic wall (staining positive with PAS and methenamine silver) can be seen containing brood capsules, scoleces and hooklets. The scoleces can be observed in sputum if rupture of a cyst occurs. Aspiration of a suspected hydatid cyst may be hazardous because of the risk of anaphylactic shock.