Lymph nodes' capsular naevi are associated with high naevus count in melanoma patients: a case-control study.

Capsular naevi (CNs) in lymph nodes (LNs) are relatively common, occurring in 3-22% of patients who undergo LN surgery for melanoma. Naevus count is one of the principal risk factors for melanoma, as well as a prognostic factor in melanoma patients. However, little is known about the occurrence of CN in melanoma patients on the basis of their naevus count. A case-control study was performed, to look at the naevus count differences between CN-positive and CN-negative melanoma patients. Cases (CN positive) were matched for age, sex and Breslow thickness with controls (CN negative). Total naevus count was recorded at diagnosis and compared between the two groups. This study was conducted in a tertiary referral academic centre for skin cancer. Twenty-two positive CN patients were matched with 22 negative CN patients. The mean Breslow thickness was 2.66 mm (range: 0.6-9). Positive CN patients were significantly associated with an increasing naevus count on their skin (P=0.02). Patients with more than 100 naevi reported an odds ratio of 7.78 on having a CN compared with patients with fewer than 50 naevi on their skin (P=0.02). An increased melanocytic migration to LNs might be the reason for the association between CNs and a high number of melanocitic naevi on the skin. This could shed some light on the physiology of melanocytes and could be an easy way to predict patients at greater risk of having CNs.