Museum specimens represent a valuable resource for helminthological research. We examined formalin-fixed livers preserved for periods in excess of 50 years from naturally infected pigs in archival material from the Helminthological Collection of the Oswaldo Cruz Institute (CHIOC), Oswaldo Cruz Foundation (FIOCRUZ). Microscopic examination revealed evidence of parasites in unilocular cystic structures containing a bladder worm vesicle lined with a thin laminated membrane. The inner germinal layer contained parasite debris and a proteinaceous hydatid-like fluid. The hepatic parenchyma showed a dense inflammatory infiltrate near the cyst, thick-walled arterial vessels, and occasionally necrosis. The adjacent hepatic parenchyma showed inter- and intra-lobular thin fibrosis, inflammatory cell infiltration and occasionally necrosis. Other histo-pathological sections showed a thick laminated wa...