Chronic bacterial and parasitic infections and cancer: a review.

BACKGROUND A relatively underestimated facet of infectious diseases is the association of chronic bacterial and parasitic infections with cancer development. Therefore, we sought to evaluate the evidence regarding the association of such infections with the development of malignancy, excluding the overwhelming evidence of the association of Helicobacter pylori and cancer. METHODOLOGY We searched Pubmed, Cochrane, and Scopus without time limits for relevant articles. RESULTS There is evidence that some bacterial and parasitic infections are associated with cancer development. The level of evidence of this association varies from high to low; in any case, a long time interval is mandatory for the development of cancer. A high level of evidence exists for the association of Salmonella Typhi with gallbladder and hepatobiliary carcinoma; Opisthorchis viverrini and Clonorchis sinensis with cholangiocarcinoma; Schistosoma hematobium with bladder cancer; chronic osteomyelitis with squamous cell carcinoma of the skin; and hidradenitis suppurativa with squamous cell carcinoma of the skin. In contrast, the level of evidence regarding the association of Chlamydia spp. with cancer is low. Mycobacterium tuberculosis is associated with lung cancer, albeit probably not etiopathogenetically. CONCLUSIONS A considerable number of bacterial infections and parasitic infections are associated with the development of cancer. Further research into recognizing additional associations of bacterial and parasitic infections with cancer is mandatory.