The familial dysplastic nevus syndrome. Natural history and the impact of screening on prognosis. A study of nine families in the Netherlands.

Since 1982, nine families with the dysplastic nevus syndrome have been identified in the Leiden area (The Netherlands). A total of 50 primary melanomas were diagnosed in 38 persons. Nineteen of these melanomas had been diagnosed before the start of the screening programme (category I), 11 were detected at the initial examination of the families (category II), and 20 were found during the course of follow-up (category III). To assess the effect of screening, we compared these categories with respect to the developmental stage of the melanomas. One of the 19 melanomas in category I, two of the 11 in category II and seven of the 20 in category III were melanoma in situ. The average thickness of the invasive melanomas in categories I, II and III was 1.75, 0.80 and 0.54 mm respectively. Sixteen of the 19 melanomas in category I (84%) were Clark III or IV, whereas 15 of the 20 melanomas in category III (75%) were Clark I or II. From these findings it may be concluded that screening can lead to the detection of melanomas at an earlier stage, which in turn can permit curative treatment and improvement of both prognosis and life expectancy. The need for supervision based on central registration of affected families to guarantee the continuity of screening is discussed.