Purpose: Melanocytic nevi in lymph nodes (NNs) are an important histological differential diagnosis of initial sentinel lymph node (SN) metastasis in melanoma. Our aim was to associate NN in SNs with clinicopathologic features and survival rates in 1 250 patients with SN biopsy for melanoma. Methods: To compare patients with present and absent NN, we used Fisher's exact test, Mann-Whitney U test, and multivariate logistic regression models in this retrospective observational study based on a prospectively maintained institutional database.Results: NN prevalence in axillary, cervical, and groin SNs was 16.5%, 19.4%, and 9.8%, respectively. NN were observed in combination with all growth patterns of melanoma, but more frequently when the primary was histologically associated with a cutaneous nevus. We observed a decreasing NN prevalence with increasing SN metastasis diameter. Multiple logistic regression determined a significantly increased NN probability for SNs of the neck or axilla, for individuals with ≥50 cutaneous nevi, midline primary melanomas, and for individuals who reported non-cutaneous malignancies in their parents. Cancer in parents was also significantly more frequently reported by melanoma patients who had more than 50 cutaneous nevi. In SN-negative patients, NN indicated a tendency for slightly lower melanoma-specific survival.Conclusions: We found a highly significant association between NN diagnosis and multiple cutaneous nevi and provided circumstantial evidence that cutaneous nevi in the drainage area of lymph nodes are particularly important. The trend toward lower melanoma-specific survival in SN-negative patients with NN suggests that careful differentiation of SN metastases is important.

Summary Background and objectives Asymmetrical distribution of melanomas in favor of the left body half has been repeatedly described. Patients and methods In a prospective cross‐sectional study, we investigated the distribution of melanocytic nevi between the left and right halves of the body in 702 patients. In 2,004 consecutive cases with melanomas, we retrospectively determined left to right (L/R) ratios of primary melanomas, lymph node metastases, and melanocytic nevi in sentinel lymph nodes (SN). Results The L/R ratios for cutaneous nevi and melanomas were 1.23 (95 % confidence interval [CI] 1.12–1.36) and 1.6 (95 % CI 1.37–1.88), respectively. In both cutaneous nevi and melanomas, the left‐sided excess was mainly found in intermittently light‐exposed skin. Of the nevus patients, 92.4 % were right‐handed. Breslow thickness and rates of ulceration did not differ significantly between the two body halves. Conclusions Melanocytic nevi and melanomas are more frequently found on the left body half. We assume asymmetric solar radiation as the causative factor. The vast majority of right‐handed people might unconsciously align their posture during outdoor activities so that the light falls in from the left. This avoids shadow cast by the dominant arm, shoulder, or head.

Purpose Melanocytic nevi in lymph nodes (NNs) are an important histological differential diagnosis of initial sentinel lymph node (SN) metastasis in melanoma. Our aim was to associate NN in SNs with clinicopathologic features and survival rates in 1, 250 patients with SN biopsy for melanoma. Methods To compare patients with present and absent NN, we used Fisher's exact test, Mann–Whitney U test, and multivariate logistic regression models in this retrospective observational study based on a prospectively maintained institutional database. Results NN prevalence in axillary, cervical, and groin SNs was 16.5%, 19.4%, and 9.8%, respectively. NN were observed in combination with all growth patterns of melanoma, but more frequently when the primary was histologically associated with a cutaneous nevus. We observed a decreasing NN prevalence with increasing SN metastasis diameter. Multiple logistic regression determined a significantly increased NN probability for SNs of the neck or axilla, for individuals with ≥ 50 cutaneous nevi, midline primary melanomas, and for individuals who reported non-cutaneous malignancies in their parents. Cancer in parents was also significantly more frequently reported by melanoma patients who had more than 50 cutaneous nevi. In SN-negative patients, NN indicated a tendency for slightly lower melanoma-specific survival. Conclusions We found a highly significant association between NN diagnosis and multiple cutaneous nevi and provided circumstantial evidence that cutaneous nevi in the drainage area of lymph nodes are particularly important. The trend toward lower melanoma-specific survival in SN-negative patients with NN suggests that careful differentiation of SN metastases is important.