DNA extraction from FFPE tissues was performed from 10 μm sections after careful microdissection. DNA extraction was performed using Ultraprep tissue DNA kit (AHN Biotechnologie, Nordhausen, Germany) following the manufacturer’s instructions. The genetic characterization of part of the tumors regarding BRAF, NRAS and TERT promoter mutations (TERTp) had been reported previously; mutations were screened as previously described (32, 33, 34).