The predisposing factors seems to suggest an infective (transmissible) agent to be linked to causation and the human papilloma virus is the agent that has been most firmly implicated. It is certainly not the case that infection with this agent is always carcinogenic, but it is a ‘trigger’ on the steps to carcinogenesis. Other factors that have been related to a higher incidence of the disease are smoking and immunosupression: e.g. renal transplant recipients have a higher risk. Once the cancerous changes occur, there is a pre-invasive stage (CIN) which precedes the more dangerous invasive cancer stage (when the cancer cells have breached the basement epithelium of the cervix and hence gained access to blood vessels/potential routes of spread). This pre-invasive stage can last for years and it is for this reason that the screening programme is so effective because detction at this stage allows pre-emptive cure of the whole condition.
