Trends in the diagnosis and clinical features of melanoma in situ (MIS) in US men and women: A prospective, observational study

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.

Keywords: age; anatomic sites; epidemiology; gender; incidence; invasive malignant melanoma; lentigo maligna; melanoma; melanoma in situ; melanoma screening; occupational cohorts.

Figure 1. Age-adjusted incidence of melanoma overall, MIS and IMM in (A) women (NHS) and (B) men (HPFS) during the follow-up period

Figure 1 shows that MIS incidence increased over the follow-up period among both women and men; the incidence of MIS increased at a greater rate than that of IMM. For women, the absolute incident cases of MIS first exceeded that of IMM during 2001–02. Among men, the absolute incident cases of MIS first exceeded that of IMM during 2007–08. *MIS, melanoma in situ; IMM, invasive malignant melanoma

Figure 2. Distribution in anatomic sites of MIS and IMM in women (NHS) and men (HPFS)

Figure 2 shows that among men diagnosed with MIS, 39% of lesions were found on the head and neck, 40% on the trunk, 15% on the upper extremities, and 6% on lower extremities, whereas in men diagnosed with IMM, 23% were found on the head and neck, 51% on the trunk, 14% on the upper extremities, 12% on the lower extremities. Among women, 25% of MIS were found on the head and neck, 29% on the trunk, 26% on the upper extremities, 21% on lower extremities, compared to IMM, where 10% were found on the head and neck, 31% on the trunk, 25% on the upper extremities, 34% on the lower extremities. (Illustrations by Iris Fung) *MIS, melanoma in situ; IMM, invasive malignant melanoma