Abstract
BACKGROUND: The incidence of melanoma in situ (MIS) is increasing, but little is known about its clinical and epidemiologic features. OBJECTIVE: We sought to determine trends in diagnosis and clinical features of MIS. METHODS: Incident cases of melanoma were collected prospectively from the Nurses' Health Study (1976-2010) and Health Professionals Follow-up Study (1986-2010). RESULTS: MIS incidence increased from 2 to 42 per 100,000 person-year among women, and from 11 to 73 per 100,000 person-year among men, exceeding the rate of increase of invasive melanomas. Melanoma mortality initially increased during the follow-up period then plateaued. Men were more likely than women to develop in situ melanomas on the upper half of the body (P < .001). Invasive melanomas were diagnosed at a younger age than MIS (P < .001), and were more likely to be found on the lower extremities than MIS (P < .001). LIMITATIONS: This is a strictly descriptive study without examination into mechanisms. CONCLUSION: We found epidemiologic and clinical differences for in situ and invasive melanomas, which support further examination into the variations in etiologic pathways. The lack of improvement in mortality despite the increase in detection of in situ relative to invasive lesions further highlights the need to improve invasive melanoma-specific clinical screening features.