Tumor size difference observed in azoxymethane‐treated KK‐Ay/TaJcl (KK‐Ay) and KK/TaJcl (KK) mice at the age of 25 weeks. (a) Azoxymethane‐developed tumors were divided into three groups by longitudinal diameter, 1–<5 mm, 5–<10 mm, and ≥10 mm. (b) Tumor volume was calculated using the formula, V = length × diameter (short) × diameter (long). ■, KK‐Ay mice; □, KK mice. Data are mean ± SD. *P < 0.05, **P < 0.01 vs tumor volume of KK mice.