Men1+/+ and Men1+/- male mice were monitored for cancer development and examined by histology between 18 and 26 months. a Number of mice of each histological category over the total number of the mice examined. The percentage of mice in each histological category is shown in parentheses. For each mouse, only the most severe type of lesion was taken into account. For this reason, mPINs observed in four mice having carcinoma lesions were not counted in this table. * p = 0.0266 (Fisher's exact test).