AREG and alcohol drinking: While risk factors such as smoking and alcohol abuse had no influence on AREG expression level, it was linked to tumor size and differentiation grade as large tumors (T3-T4) had higher AREG expression than smaller tumors (T1-T2) (Table 1), and well-differentiated tumors (G1-G2) had higher AREG expression than poorly differentiated tumors (G3-G4) (Table 1).