Early Detection of Subungual Melanoma In Situ: Proposal of ABCD Strategy in Clinical Practice Based on Case Series

Background Prevalence of subungual melanoma (SUM) in Asian population is relatively high and early clinical detection improves both quality of life and survival. Objective We sought to establish screening strategy for SUM in situ. Methods We retrospectively reviewed medical records of 8 patients pathologically diagnosed as SUM in situ between January 2015 and September 2016. Results All patients in our study were adults and had solitary lesion. In all cases, longitudinal melanonychia as well as background pigmentation in entire nail plate was observed. Seven (87.5%) cases had periungual pigmentation. Clinical features of SUM in situ can be summarized according to new criteria categorized under initial letters of alphabet, namely nail ABCD of SUM in situ; "A" stands for adult age (age >18 years); "B" for brown bands in brown background; "C" for color in periungual skin; "D" for one digit. Our strategy was to suspect SUM in situ if solitary longitudinal melanonychia in adult was satisfying either "B" or "C" in ABCD. All cases were suspected as SUM in situ under nail ABCD rule, and histological examination confirmed diagnosis. Sensitivity and specificity of nail ABCD was 100% and 96.6%, respectively, regarding our previously published 18 SUM in situ and unpublished 28 nail matrix nevi cases as well as 8 SUM in situ presented here. Conclusion ABCD rule is simple and sensitive clinical strategy for early detection of SUM in situ.