Association of clinicopathological features of melanoma with total naevus count and a history of dysplastic naevi: a cross‐sectional retrospective study within an academic centre

Summary Background High naevus count ( HNC ) (≥ 50 naevi) and presence of dysplastic naevi ( DN ) are risk factors for malignant melanoma ( MM ); however, MM s also occur in patients with low naevus count ( LNC ) (< 50 naevi) and in patients without DN . Little is known about differences between MM s in these groups. Aim To characterize the clinicopathological differences between MM s in patients with HNC and those in patients with LNC , with or without biopsy‐proven DN . Methods This was a cross‐sectional retrospective chart review of 281 patients with MM seen between April 2013 and March 2014 at an academic pigmented lesion clinic (Boston, MA , USA ). Results Patients with LNC MM s were diagnosed at an older age (51 vs. 41 years, P < 0.001, OR = 0.95, 95% CI 0.93–0.97), with more aggressive MM features, including greater Breslow thickness (1.1 vs. 0.8 mm, P = 0.01), more mitoses (2 vs. 1 mitoses/mm 2 , P < 0.001), lower rate of superficial spreading subtype (58 vs. 78%, P < 0.01, OR = 2.57, 95% CI 1.31–5.03) and higher MM stage ( P < 0.001), compared to patients with HNC . Patients with DN had similar trends as those in patients with HNC described above, and in addition, were more likely to have a truncal MM (55 vs. 39%, P < 0.01, OR = 1.97, 95% CI 1.22–3.18) with less ulceration (13 vs. 29%, P < 0.01, OR = 0.36, 95% CI 0.19–0.71). Patients without DN were more likely to have a history of a non‐ MM skin cancer (32 vs. 19%, P = 0.01, OR = 0.49, 95% CI 0.28–0.85) and an amelanotic MM (33 vs 21%, P = 0.03, OR = 0.55, 95% CI 0.31–0.96). Conclusions Patients with LNC may develop MM s with more aggressive features at an older age than patients with HNC . A history of biopsy‐proven DN reveals distinct MM differences compared to patients without DN .