Gastrointestinal Neoplasia Associated with Bowel Parasitosis: Real or Imaginary?
Several parasitic species are well known to have carcinogenic properties, namely;Schistosoma hematobium(squamous cell carcinoma of the bladder) and the liver flukesOpisthorchisandChlonorchis(cholangiocarcinoma). A large number of parasites are known to colonize the gastrointestinal tract. We sought to review the evidence that implicates these parasites in gastrointestinal neoplasia.Schistosoma japonicum, which is endemic primarily in east Asia, has been shown in multiple studies to convey a mildly increased risk of colorectal adenocarcinoma. The data supporting a causative role forSchistosoma mansoniin colorectal or other neoplastic processes are less convincing, limited primarily to small case-control studies and case series. Reports of possible associations between other gastrointestinal parasites (e.g.,E. histolyticaandA. lumbricoides) and neoplasia may be found in the literature but are limited to individual cases. We conclude that, other thanS. japonicumand to a lesser extentS. mansoni, there is little evidence of an association between gastrointestinal parasites and neoplasia.