A, B: Fertile hydatid cyst with high viability protoscoleces (PSC) are characterized by a germinal layer with PSC, followed by a thick laminated layer and an adventitial layer composed of collagen fibers that detach from the laminated layer (arrows). C, D: Fertile hydatid cysts with low viability PSC feature the same germinal and laminated layer characteristic of high viability fertile hydatid cysts, but have an adventitial layer composed of inflammatory cells that are tightly attached to the laminated layer (arrows). E, F: Infertile hydatid cysts have little to none germinal layer cells with a thin laminated layer, the adventitial layer is composed palisading foamy macrophages, multinucleated giant cells and lymphoid follicles. This inflammatory infiltrate is tightly attached to the laminated layer (arrows). G, H: Small hydatid cysts (i.e. <1 cm) feature the same histological characteristics as infertile cysts. Size bar: A: 400 μm, B: 200 μm, C: 400 μm, D: 200 μm, E: 400 μm, F: 100 μm, G: 400 μm, H: 200 μm.