Entamoeba Histolytica Infesting Colonic Malignancy: First Series of Four Cases

Entamoeba histolytica infections of the gastrointestinal tract are common in the developing world. Only two isolated cases of colonic amoebiasis with colon carcinoma have been described in literature. Here, we describe unique series of four cases showing coexistence of Entamoeba trophozoites with colon cancer. The organisms were demonstrated by Periodic acid Schiff (PAS) stain, which highlighted the trophozoites. Three of the patients were treated with metronidazole and two underwent subsequent resection and adjuvant chemoradiotherapy. Importance of diagnosing coinfection lies in view of immunocompromised state of the cancer patients, most of whom also receive adjuvant chemotherapy and radiotherapy. In such a scenario, if Entamoeba coinfection is not treated, it may lead to complications such as spread of organisms to the brain, liver, lungs and pericardium. The series emphasizes that a high index of suspicion for co-existing parasites is needed in colon cancers, especially in endemic countries.