A case report of colonic Ameboma mimicking colon cancer in an immunocompromised patient

Abstract

Introduction and importance: Entamoeba histolytica is an anaerobic protozoan. It infects humans causing Amoebiasis. Most infections are asymptomatic; however, clinical manifestations include intestinal or extraintestinal. In rare instances, patients can present with Ameboma: a mass of granulation tissue consisting of a core of inflammation with peripheral fibrosis related to chronic amoebic infection usually found in the cecum/ascending colon.

Presentation of case: A 50-year-old patient presented with signs and symptoms of bowel obstruction. He had raised inflammatory markers and was HIV positive on treatment and virally suppressed. At laparotomy a hepatic flexure stricture with desmoid reaction, and wall thickening with induration at the mesenteric border of mid-transverse colon was found, with disseminated nodular disease. Histology confirmed entamoeba histolytica infection.

Discussion: The parasite exists in two forms: a cyst stage and a trophozoite stage: the form causing invasive disease. The presentation of intestinal amoebiasis ranges from an asymptomatic carrier state, colitis, to abscess formation and bowel perforation The management principles: to eliminate the invading trophozoites and eradicate the organism's intestinal carriage and manage complications such as obstruction, fulminant colitis, or toxic megacolon with surgery.

Conclusion: This case identifies a rare cause of bowel obstruction in a patient without a travel history. Even with the lack of significant risk factors other than HIV, clinicians should be aware of the infective causes of colonic mass/stricture outside of malignant causes. Entamoeba histolytica is an infection of impoverished communities in developing countries, it should remain high on our differential for tumour-like granulation tissue in the colon.

Keywords: Amoebiasis; Bowel obstruction; Case report; Immune compromise; Infectious disease.

Fig. 1

CT showing intussuception.

Fig. 2

Multiple ulcers are noted throughout the segment of colon. There are multiple well defined discreet ulcers with irregularly shaped borders. There is a yellow-to-white slough overlying the ulcer base. The intervening mucosa is not inflamed. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Multiple ulcers are noted throughout the segment of colon. There are multiple well defined discreet ulcers with irregularly shaped borders. There is a yellow-to-white slough overlying the ulcer base. The intervening mucosa is not inflamed. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

A low power (4× magnification) view showing a colonic ulcer forming an inflammatory mass.

Fig. 5

A 40× magnification view confirming amoebic colitis. Infiltrating trophozoits with abundant eosinophilic cytoplasm and a distinctive round nucleus can be seen.