In a retrospective study we measured the incidence of internal malignancy in patients diagnosed as having Bowen's disease, in Northern Ireland, between 1970 and 1983. Data on 157 patients were obtained from hospital notes, death certificates, the Northern Ireland Cancer Registry and the patients' general practitioners. There was a preponderance of females with Bowen's disease with a female to male ratio of 2.8: 1.

The incidence of internal malignancy was significantly greater in patients with Bowen's disease than that expected for the general population, suggesting that these patients should be screened for occult malignancy. Patients with multiple areas of Bowen's disease did not appear to be more at risk of internal malignancy than those with a single lesion.