Prevalence of subungual melanoma in patients with cutaneous malignant melanoma: a systematic review and meta-analysis.

Subungual melanoma (SUM) is a rare type of cutaneous malignant melanoma (CMM), associated with poor prognosis, while data regarding its prevalence are scarce. We sought to provide a comprehensive systematic review and meta-analysis of the prevalence rates of SUM among all types of CMM, considering certain demographic and clinical characteristics. The MEDLINE electronic database was searched systematically to identify eligible studies providing prevalence rate estimates of SUM in patients with CMM. Included studies were further analyzed to estimate the relative prevalences of SUM according to study design, study years, geographic region and sex distribution. Twenty-eight studies met the inclusion criteria. The overall SUM prevalence was 1.9% [95% confidence interval (1.5-2.3%)]. The prevalence of SUM did not differ significantly between population- vs. hospital-based studies and remained stable over time. However, it was found to be significantly higher in Asians compared to patients of other geographical regions as well as in studies with more men than women compared to those with female preponderance (p<0.001). In all, the overall SUM prevalence among all subtypes of CMM was estimated at 1.9%, without significant changes over time, and was found to exhibit significant variability between subgroups of different geographical regions.