Invasive amebiasis and ameboma formation presenting as a rectal mass: An uncommon case of malignant masquerade at a western medical center.

A 54-year-old man presented with rectal pain and bleeding secondary to ulcerated, necrotic rectal and cecal masses that resembled colorectal carcinoma upon colonoscopy. These masses were later determined to be benign amebomas caused by invasive Entamoeba histolytica, which regressed completely with medical therapy. In Western countries, the occurrence of invasive protozoan infection with formation of amebomas is very rare and can mistakenly masquerade as a neoplasm. Not surprisingly, there have been very few cases reported of this clinical entity within the United States. Moreover, we report a patient that had an extremely rare occurrence of two synchronous lesions, one involving the rectum and the other situated in the cecum. We review the current literature on the pathogenesis of invasive E. histolytica infection and ameboma formation, as well as management of this rare disease entity at a western medical center.