CD6 and neoplasm: Much of this game is played via the selective expression of bona fide CD6 ligands (CD166/ALCAM, CD318/CDCP1, CD44, and Galectins 1/3) by cancer cells of many lineages, adding to tumour versus normal tissue specificity and offering the opportunity to readily target these ligands therapeutically while minimising on-target off-tumour toxicity.