At a molecular level, the solid component is enriched in the expression of cancer stem cell markers ATP-binding cassette G2 (ABCG2) and multidrug resistance associated protein 1 (MRP1) that were absent or significantly lower expressed in the papillary component of the same tumor, whereas they are frequently overexpressed in ATC and are related to adverse clinical outcomes [28,29]. This evidence concerns the gene ABCG2 and neoplasm.