E. histolytica cyst is usually transmitted by the fecal-oral route (through contaminated drinking water or food) or by direct contact with infected individuals. Following transmission, E. histolytica trophozoites undergoes excystation in the small intestine, after which it migrates to the large intestine using pseudopods. The trophozoites invades the intestinal mucosa and migrates into the bloodstream. Simultaneously, they form resistant cysts in the large intestines that are then excreted in human stools. E. histolytica trophozoites secrete proteases and glycosidases to degrade the intestinal layers. Once cellular degradation occurs, upregulation of IL-8 and TNF-alpha results in the recruitment of neutrophils, macrophages, and eosinophils. The host immune system does not usually result in adequate destruction of the E. histolytica trophozoite, and the parasite continues to invade until it reaches the bloodstream, whereby it can then migrate to other organs and cause multisystem disease. On gross pathology,<unk>  may be characterized by wavy surface epithelium and formation of nodular and irregular ulcerations. On microscopic pathology, flask-shaped ulcers are characteristic, but interglandular ulcerations, hyperemia, mucosal thickening, reactive glandular hyperplasia, and neutrophilic infiltration are common findings. In late stages,<unk>  often results in tissue fibrinoid necrosis and formation of granulation tissue.
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