In addition, we have found that high-grade MTC upregulates ASCL1, DLL3, and SOX2, a gene signature akin to SCLC molecular subgroup A. Taking into consideration our results about the impact of DLL3 expression on prognosis, both desmoplasia and DLL3 overexpression should be explored as predictors of aggressive disease and poor outcomes. This evidence concerns the gene SOX2 and medullary thyroid gland carcinoma.