Technological advances have provided the means whereby several cancers can be screened by a range of devices. These include the use of automated cytology scanning for abnormal cells in cervical smears, mammographic techniques for the early detection of breast tumours, and the use of genetic screening methods to detect various cancers which are to a greater or lesser degree genetically determined (e.g. some breast and colonic cancers) (see ‘Screening: cancer’). Such developments notwithstanding, there remains a potential role for self-examination procedures since (a) there remain many cancers for which technological procedures are not available (b) some procedures involve elements of risk, for example, the use of ionizing radiation in mammography, which limit the frequency with which they can be applied and (c) practical constraints may limit the applicability of the procedures to only a subset of those at risk.

For example, in the UK some 1 in 12 women will have breast cancer at some point in their lives, but for a number of reasons, (including logistical reasons and variation in the characteristics of the disease in women of different ages), screening by invitation is currently available only once every three years, and only to women in the 50–64 age group (with plans for extension up to age 70 in the near future). Yet breast cancer is far from unknown in younger women, and nor is it unknown for a tumour to grow to a significant size in less than the three-year time interval between successive examinations.