A Case Report on Schistosoma and Gastric Cancer: Association or Causation?

The association of gastric cancer with parasitic infestation is rather uncommon. We report a case of gastric cancer accompanied by Schistosoma (S.) mansoni, incidentally found in histopathological examination. While this coexistence may be incidental, the rarity of such a finding prompts consideration of a possible pathophysiological link. A 39-year-old Sudanese man presented with epigastric pain, significant weight loss of 20 kg over six months, and dyspepsia, without nausea or vomiting. His medical history included diabetes mellitus and previous tobacco use. Laboratory investigations revealed anemia, hypoalbuminemia, and elevated tumor markers, including carcinoembryonic antigen (CEA) and cancer antigen 125 (CA 125). Endoscopic evaluation identified a nodular, friable mass with ulceration on the lesser curvature of the stomach, and biopsy confirmed signet-ring cell adenocarcinoma with Schistosoma infestation. Immunohistochemistry revealed HER2 negativity, intact mismatch repair (MMR), and PD-L1 positivity. Computed tomography (CT) imaging demonstrated advanced gastric cancer (cT4cN3M1). Management included palliative chemotherapy, genetic counseling, potential pyloric stenting, and treatment of schistosomiasis. This case illustrates the exceedingly rare histological coexistence of S. mansoni and diffuse-type gastric cancer, underscoring the complex and poorly understood relationship between infectious agents and gastric malignancy. Further research is warranted to elucidate the potential role of S. mansoni in gastric cancer pathogenesis.