Therefore, GREB1 expression in HB is correlated with β-catenin signaling activity but not always be associated with mutations and deletions at exons 3 and 4 of CTNNB1. Other CTNNB1 mutations or CTNNB1 mutation-independent activation of β-catenin signaling could occur in these cases. This evidence concerns the gene CTNNB1 and hemoglobin measurement.