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

Abstract

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.

Amoebome-cancer du côlon. Les pièges diagnostiques à éviter

“…1). Ces aspects macroscopiques mimant un cancer colique ont été rapportés par Hardin et al [9] qui ont décrit dans un cas clinique une masse ulcéronécrotique du rectum et du caecum. Les biopsies avaient mis en évidence, comme chez notre patiente, un infiltrat lymphoplasmocytaire important associé à des amibes hématophages (Fig.…”

“…Dans l'observation de Hardin et al [9], il a fallu quatre semaines de traitement aux imidazolés pour aboutir à une disparition des signes cliniques et des lésions rectales et caecales.…”

Polymorphonuclear Neutrophil Infiltration Intensity as Consequence ofEntamoeba histolyticaDensity in Amebic Colitis

“…It has been proposed that neutrophils, by releasing lysosomal enzymes, play a major role in the tissue damage seen in amebiasis [23][24][25]. The clinical spectrum of colorectal amebiasis ranges from an asymptomatic carrier state to fulminant necrotizing colitis with bleeding and perforation [26]. Patients with long-standing infection develop ulcerative, exophytic, inflammatory masses (amebomas) that are indistinguishable endoscopically from carcinomas and can become of considerable size, reportedly as large as 15 cm in diameter.…”

“…Patients with long-standing infection develop ulcerative, exophytic, inflammatory masses (amebomas) that are indistinguishable endoscopically from carcinomas and can become of considerable size, reportedly as large as 15 cm in diameter. Moreover, colonic amebomas may present with synchronous amebic liver abscesses, which can masquerade as advanced carcinoma of the gastrointestinal tract [26] or produce severe sepsis.…”

“…Proper diagnosis could allow prompt treatment with metronidazole, which still is the primary agent for amebic colitis (given for 5-10 d, sometimes followed by a luminal agent such as paromomycin, iodoquinol, or diloxanide furoate for 5-20 d to eradicate colonization). Surgical intervention is seldom indicated except for rare instances of acute necrotizing colitis with bowel perforation, or if the patient fails to respond to anti-amebic drugs [26].…”