Colorectal Cancer Arising From Chronic Colitis Due To Strongyloides stercoralis

Abstract

Introduction: Rarely pathogenic organisms, including parasites, can act as carcinogens. To our knowledge, there are no reported cases regarding the association between a Strongyloides stercoralis infection and colon cancer. A 47-year-old South American man with vitiligo and iron deficiency anemia presented with fatigue and weight loss. He denied diarrhea, vomiting, or family history of malignancy, and there was no overt GI bleeding. His last esophagogastroduodenoscopy (EGD) and colonoscopy was 6 years prior, in his home country of Columbia, and reported as normal. He was hemodynamically stable, and physical exam revealed vitiligo and guaiac positive stool. On blood a hemoglobin of 3.1 gm/dL and eosinophilia was seen. Our differential at the time included a possible autoimmune disorder, celiac disease, inflammatory bowel disease, or parasite infection. On EGD he had normal appearing mucosa and biopsies revealed Strongyloides stercoralis. On colonoscopy there was loss of haustral folds, friability, and erosions of the ascending, splenic flexure, and sigmoid colon. A 3 x 4-cm ascending colon mass was also seen. Biopsies showed invasive low-grade adenocarcinoma along with chronic colitis of the ascending, splenic flexure, and sigmoid colon. Stool studies at that time were also positive for Strongyloides stercoralis. Computed tomography (CT) scan of his chest, abdomen, and pelvis did not reveal any metastasis. Treatment was initiated with 2 doses of Ivermectin 200 mcg per kg per day and the decision of a right extended hemicolectomy with ileocolic anastomosis instead of total colectomy was made after a discussion with the patient and surgical team. Surgical pathology revealed invasive low-grade adenocarcinoma with clear margins and no lymph node involvement, stage 2b colon cancer. The patient refused any adjuvant chemotherapy. To date, surveillance colonoscopies at 6 months and 2 years have been unremarkable for colon cancer or colitis and stool studies have been negative for Strongyloides. His anemia has resolved and he has gained weight. This case illustrates the only known association of chronic colitis and colon cancer due to Strongyloides stercoralis, and that the identification of this parasite in some may warrant a more thorough GI workup.