Background Cancer develops from the transformation of normal cells into neoplastic ones in a multistage process that typically goes from a precancerous lesion to a malignant tumour. On a global scale, cancer incidence varies widely and is steadily rising. Lung cancer is the second and fourth most common cancer in men and women in Japan, respectively, contributing to growing mortality rates. In this work, we wish to know how many gene mutations are required for lung carcinogenesis in both sexes in Japan. Methods We use age-specific incidence data of lung cancer in Japanese men and women from 1985 to 2012 to construct multistage models estimating mutation rates and clonal expansion rates. We’re also looking into the function of genomic instability and the mutator phenotype in the development of lung cancer. A p-value can be used in conjunction with the chi-square test to check the hypothesis that indicates whether a mathematical model with a k-stage fits the incidence data perfectly. By means of a chi-square test we determined the number of stages in the multistage model which gives the optimal fit with respect to incidence data. Results The progression of lung cancer differs between men and women in the Japanese population. In Japan, two to nine driver mutations are commonly necessary for the development of lung cancer in both male and female patients, but in the United States, two to six gene mutations are required. The model assuming five (four) driver mutations among male (female) patients best fitted the data. Conclusions A range of lifestyles, genetic effects, and environmental exposures contribute to variances in mutation