Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: An exceptional form of hepatic alveolar echinococcosis with metastasis of the right atrium is reported. This cardiac location of the parasitosis was revealed by attacks of pulmonary embolism which produced secondary pulmonary lesions. This case suggests that pulmonary metastases of alveolar echinococcosis of the liver might be due to the migration of parasitic clots from the hepatic veins.
Antigens, Helminth