Pathological characterization of hepatic and mesenteric neotropical Echinococcosis in Brazilian Amazonian patients using light and scanning electron microscopy.

Neotropical Echinococcosis (NE) is an emerging parasitic zoonosis of significant public health concern. The disease is caused by the larval stage (metacestodes) of Echinococcus vogeli and affects humans in tropical forests of Central and South America. While clinical presentation, radiological imaging, and surgical procedures have been investigated, the pathological features of NE remain partially understood. We performed a comparative study of hepatic and mesenteric metacestodes obtained from Brazilian patients in Acre and Amazonas States during surgical procedures, using both light and scanning electron microscopy for detailed analysis. Liver metacestodes showed three characteristic layers: adventitious, laminated, and germinal. In contrast, mesenteric cysts lacked a consistent layer organization, as the adventitious layer was absent, and the laminated layer was the most prominent membrane within the cyst. Compression exerted by the metacestodes led to hepatic and mesenteric hypertension, characterized by passive hyperemia. Other features induced by hypertension included an expanded sinusoidal bed and extensive areas of hemorrhage resulting from vascular rupture and subsequent blood leakage. In conclusion, the development of mesenteric and hepatic cysts follows distinct patterns, and scanning electron microscopy proves to be a valuable investigative tool for evaluating the pathology of Neotropical Echinococcosis.