Background
The incidence of melanoma in situ is rising, but little is known about its characteristics.
Objective
To determine trends in diagnosis and clinical features of melanoma in situ.
Methods
Incident cases of melanoma were collected prospectively from the Nurses’ Health Study from 1976–2010 and Health Professionals Follow-up Study from 1986–2010.
Results
MIS incidence increased from 2 to 42 per 100,000-person-year (100KPY) among women, and from 11 to 73 per 100KPY 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 upper half of the body (p<0.001). Invasive melanomas were diagnosed at a younger age than melanoma in situ (p<0.001), and were more likely to be found on the lower extremities than in situ melanomas (p<0.001).
Limitations
This is a strictly descriptive study without examination into mechanisms.
Conclusion
We found epidemiologic and clinical differences in in situ and invasive melanomas, which support further examination into the variations in etiologic pathways. The lack of improvement in mortality despite increase in detection of in situ relative to invasive lesions further highlight the need to improve invasive melanoma-specific clinical screening features.