Clinicopathological features, vitamin D serological levels and prognosis in cutaneous melanoma of shield-sites: an update.

Intermittent sun exposure and sunburns are strongly related to the development of melanoma (MM); however, MM can also arise in non-sun exposed areas, where other biological pathways may cause the disease, with different outcomes. At the same time, evidences of serum levels of vitamin D in melanoma patients according to sun-exposed or not-sun-exposed areas are still lacking, especially if compared with the percentage of BRAF mutation. We performed a retrospective analysis with patients registered in our electronic database and an observational study in patients with a recent diagnosis of MM. Performing Kaplan-Meier product and log-rank test, median disease-free survival was 78 months in non-shield-sites (NST-MM) patients and 20.5 months in shield-sites (ST-MM) patients (p < 0.0001); also in the long term, a better behavior was observed for NST-MM (80 vs. 42 months; p < 0.0001). Among 87 melanoma patients with a recent history of MM (≤30 days), we found that ST-MM patients showed lower values of vitamin D compared with NST-MM patients. Regarding BRAF status, a BRAF mutation was present in 13 % of ST-MM and in 41 % of NST-MM. Performing Mc-Nemar test, we found a statistical significant correlation between low serum levels of vitamin D in ST-MM and low percentage of BRAF mutation (p = 0.03), as well as between serum levels of vitamin D and high percentage of BRAF mutation in NST-MM (p < 0.001). All these aspects confirm that in ST-MM, other pathways play pivotal points, if compared with NST-MM.