Objective: In the Netherlands the incidence of melanomas in situ and thin invasive melanomas is rising more quickly than that of thicker melanomas. Our aim was to gain insight into this increase and to test the hypothesis that it is attributable to over-diagnosis.
Method: We analysed data taken from the Netherlands Cancer Registry on all primary melanomas diagnosed between 1994 and 2010. We assessed trends in European standardised rates (ESR) using joinpoint analysis, and expressed these trends as estimated annual percentage change (EAPC). Thin melanomas were subdivided into four subgroups.
Results: Between 1994 and 2010, 34 156 persons were diagnosed with melanoma in situ or thin invasive melanoma. The incidence of melanoma in situ doubled during this period, with an acceleration in incidence in men from 2004, and in women from 2007. In men the ESR of thin melanoma doubled, whereby the thinnest category (< 0.25 mm) rose more quickly, but not significant compared to the other Breslow thicknesses ≤ 1 mm. In women, the ESR of thin melanomas nearly doubled, with the exception of the thinnest melanoma.
Conclusion: Between 1994 and 2010, the incidence of melanomas increased steadily. In part, this was a real rise as a result of increased exposure to ultraviolet rays. However, from 2006 the incidence of melanomas in situ and thin invasive melanomas in men has risen comparatively more quickly. This could point to over-diagnosis, but also to increased awareness, early detection, a diagnostic shift from benign to malignant lesions and changes in the Dutch health care system.