page_title: Causes of cancer
section_title: Bacteria and parasites
hierarchical_section_title: Causes of cancer / Infection and inflammation / Bacteria and parasites
caption_attribution_description: English: Histopathology of schistosomiasis haematobia, bladder Histopathology of bladder shows eggs of Schistosoma by intense infiltrates of eosinophils and other inflammatory cells. Parasite. Italiano: Campione istologico di vescica che mostra le uova di Schistosoma haematobium con infiltrazione di granulociti eosinofili. Español: Microfotografía de vejiga con esquistosomas S.haematobium mostrando grupos de huevos y eosinofilia. Lietuvių: Schistosoma haematobium kiaušiniai žmogaus šlapimo pūslėje. Urogenitalinės šistosomozės (bilharciozės) sukėlėjo kiaušiniai.
context_page_description: Cancer is a disease caused by genetic changes leading to uncontrolled cell growth and tumor formation. The basic cause of sporadic cancers is DNA damage and genomic instability. A minority of cancers are due to inherited genetic mutations. Most cancers are related to environmental, lifestyle, or behavioral exposures. Cancer is generally not contagious in humans, though it can be caused by oncoviruses and cancer bacteria. The term "environmental", as used by cancer researchers, refers to everything outside the body that interacts with humans. The environment is not limited to the biophysical environment, but also includes lifestyle and behavioral factors.
  Over one third of cancer deaths worldwide are potentially avoidable by reducing exposure to known factors. Common environmental factors that contribute to cancer death include exposure to different chemical and physical agents, environmental pollutants, diet and obesity, infections, and radiation. These factors act, at least partly, by altering the function of genes within cells. Typically many such genetic changes are required before cancer develops.
context_section_description: Certain bacterial infections also increase the risk of cancer, as seen in Helicobacter pylori-induced gastric carcinoma. The mechanism by which H. pylori causes cancer may involve chronic inflammation or the direct action of some of the bacteria's virulence factors. Parasitic infections strongly associated with cancer include Schistosoma haematobium (squamous cell carcinoma of the bladder) and the liver flukes, Opisthorchis viverrini and Clonorchis sinensis (cholangiocarcinoma). Inflammation triggered by the worm's eggs appears to be the cancer-causing mechanism. Certain parasitic infections can also increase the presence of carcinogenic compounds in the body, leading to the development of cancers. Tuberculosis infection, caused by the mycobacterium M. tuberculosis, has also been linked with the development of lung cancer.
caption: Histopathology of Schistosoma haematobium eggs within the lining of the bladder.
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