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.

Abstract

High naevus count (HNC) (≥ 50 naevi) and presence of dysplastic naevi (DN) are risk factors for malignant melanoma (MM); however, MMs also occur in patients with low naevus count (LNC) (< 50 naevi) and in patients without DN. Little is known about differences between MMs in these groups. To characterize the clinicopathological differences between MMs in patients with HNC and those in patients with LNC, with or without biopsy-proven DN. 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). Patients with LNC MMs 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/mm2 , 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). Patients with LNC may develop MMs 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.