HGS and thyroid nodule: Although these five proteins have not yet been studied in the thyroid, we found four proteins (HGS, MTPN, RPL24, and CORO7) were directly or indirectly connected with the known thyroid cancer-related proteins by the network analysis (Fig. 3d), which indicates that the feature selection by genetic algorithm has the potential to unearth the hidden essential proteins to classify thyroid nodules.