A two-year-old Labrador retriever living in the French Alps was presented with abdominaldistension, lethargy and weight loss but no other specific clinical signs. CT examination revealed alarge, cavitary liver mass invading the caudal vena cava, associated with multiple hepatic lesionsof similar appearance, lymphadenopathy and pulmonary nodules. The condition was initiallymistaken for a malignant neoplasm. However, cytologic and histologic examinations of the largest liver mass were consistent with cestodiasis and PCR testing confirmed infection with Echinococcus multilocularis. Medical treatment with albendazole was initiated. The dog remained clinicallywell for ten months following the diagnosis, but had to be euthanized because the ownershad to return to Great-Britain and the dog could not be legally imported. To the authors’ knowledge, this is the first case report, in which long-term follow-up of Echinococcus sp. infection in adog, managed medically, is described. This case also shows that medical management may be aviable option in case surgery is not feasible.