Is Colon Cancer a Consequence of Schistosomiasis: A Case Report

Abstract

Colorectal cancer is one of the most common cancers worldwide with increasing prevalence in the Asian countries. Schistosoma japonicum, an endemic trematode in these countries, has been recognized as a colonic carcinogen. We report a case of resected rectal adenocarcinoma in a Filipino lady whose pathology was significant for Schistosoma eggs. A 69 year old Filipino lady with a history of resected left-sided invasive ductal carcinoma of breast presented with complaints of chronic lower abdominal discomfort, constipation alternating with diarrhea and weight loss for around 10 months. Physical examination and laboratory tests were noncontributory other than a normocytic anemia with hemoglobin of 11.6 gm/dl. Subsequent colonoscopy revealed a malignant appearing obstructive mass in the distal sigmoid colon (figure A). Magnetic resonance imaging showed bladder wall thickening with poor visualization of other structures due to limited oral contrast. An exploratory laparotomy successively resulted in anterior pelvic exenteration, sigmoid resection with primary anastomosis and ileal conduit creation for sigmoid cancer invading bladder. Her pathology demonstrated invasive moderately differentiated adenocarcinoma and numerous Schistosoma eggs in the colon, ovaries, posterior cul-de-sac and pelvic wall (Figure B). The parasitic infection was treated with praziquental and a stool microscopic examination in 3 weeks was negative for ova and parasites. Schistosomal infestation has been implicated by International Agency for Research on Cancer as an etiology for several cancers such as colon, liver and bladder. Schistosoma is known to trigger chronic inflammatory changes and epithelial hypertrophy, which sets foundation for dysplasia and consequent carcinoma. Production of genotoxic mediators such as reactive oxygen species and cytokines are proposed to play a role in dysregulation of oncogenes and oncogene suppressors. Our patient was from the Philippines, where prevalence rates of Schistosoma japonicum have been reported to be as high as 28%. It is likely to be the etiology of colon cancer in our patient. In Western countries, physicians should be aware of such associations when dealing with immigrants of endemic areas to facilitate early diagnosis and management. The causal relationship and benefit of screening and treatment for Schistosoma is a subject of debate and needs further research.1496_A Figure 1. Colonoscopy revealing a malignant appearing obstructive mass at the distal sigmoid colon1496_B Figure 2. Colonoscopy revealing a malignant appearing obstructive mass at the distal sigmoid colon1496_C Figure 3. Histopathology of resected sigmoid colon revealing Schistosoma eggs and moderately differentiated adenocarcinoma