SMAD3 and neoplasm: High-risk tumor depths (≥4 mm) demonstrated a markedly significant negative dependence on both phosphorylated SMAD2 (C.C −0.214; p = 0.001) and SMAD3 (C.C −0.200; p = 0.002), which is consistent with a tumor-suppressive role for SMAD2/3 activators in cSCC [41].