Mutational landscape in squamous cell carcinoma of the nail unit

Squamous cell carcinoma (SCC) is the most common malignancy of the nail unit. Pathogenetic mechanisms are yet to be determined, and a deeper molecular characterization of this disease is still necessary. The aim was to obtain a molecular characterization of NU SCC samples using an NGS approach to identify the genetic drivers involved in this tumor. The presence of HPV infection was also assessed. Furthermore, the mutational status was correlated with specific clinical-pathological features for a better insight into the carcinogenesis of this uncommon tumor. We analysed twenty paraffin-embedded nail unit SCC samples from patients diagnosed with primary SCC of the nail unit by next genome sequencing. In the 20 tested samples, the neoplastic cells enrichment ranged from 10% to 50% (mean value: 25.7%). In 14/20 cases (70.0%), at least one mutation was detected; whereas in the other six cases (30.0%), no alterations were observed (‘wild-type/WT cases’). Overall, a total of 23 mutations were identified in the 20 specimens. TP53 was the most mutated gene (6/20 cases, 30.0%), while cKit, GNAS, EGFR, DICER1 and CTNNB1 were observed in one sample each (5.0%). No clinical-pathological parameters (age, sex, depth of invasion-DOI, histological subtype, grading and HPV) were significantly associated with the mutational status. The nail unit SCC mutational landscape appeared to be heterogeneous, favouring the hypothesis of a complex pathogenesis and an interaction of multiple elements, including HPV infections. This wealth of information undoubtedly improves our understanding of SCC biology.