An Unusual Case of Rectal Ameboma Masquerading as Anorectal Carcinoma

Entamoeba histolytica is a major cause of diarrhea in the developing countries and it can present with a wide range of gastrointestinal symptoms depending on the phase of the infection. Here is a case of 70-year-old female patient with history of Type 2 diabetes, hypertension, hypothyroidism, and chronic kidney disease (stage 3), presented to us with progressive anorectal pain, bleeding per rectum, large bowel type of diarrhea, and anorexia since 2 months. Clinical and radiological examination was suggestive of a mass lesion—likely neoplastic. Sigmoidoscopy showed an ulcero-proliferative mass in anorectal area ([Fig. 1]). Histopathology showed presence of dense necrotizing fibrinopurulent exudate admixed with rounded large trophozoites with ingested red blood cells confirming to the morphology of Entamoeba histolytica ([Fig. 2]). In view of high suspicion for anal canal malignancy, colonoscopy was done and repeat biopsy was taken. Rest of the colon was normal. Repeat biopsy was also suggestive of similar result as before. After a 4-week course of metronidazole along with luminal amebicides led to the resolution of the symptoms and the mass lesion. Amebomas of the large intestine are a rare condition that occurs in 1.5% of all cases of invasive amoebiasis, characterized by mass-like lesion with granulation tissue and fibrosis, usually found in ascending colon or caecum. Detailed history and histopathological examination is needed to diagnose and differentiate from malignant anorectal lesion as amoebiasis is completely curable and avoid surgery.