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tion of prognosis for survival. Hence, precise measurement of tumor size is crucial to improve stratification of lung cancer in the future. Based on these clinical backgrounds, we propose a new clin-ical T staging based on a GGO component in many reports, because we believe that the T staging should be simple, useful and reproducible to reflect the prognosis of lung cancer. Based on our clinical research, 5y-OS of part-solid lung cancer with 56Figure 4　Radiological findings of part-solid lung adenocarcinomas with a solid component size that is difficult to measure: GGO with scattered consolidations (A, B), GGO with island shaped consolidations (C, D), or GGO mimicking organizing pneumonia (E, F).Figure 5　Proposed clinical T category based on the presence of a GGO component11, 36).GGO was more than 90% regardless of whole tumor size or solid component size. Therefore, we believe that part-solid lung cancer could be demonstrated as c-T1a despite their tumor size. In contrast, Tumor size has a great impact on the prognosis only in radiological pure-solid lung cancer. There-fore, tumor size effect should be exclusively applied to the radiological solid lung cancer without GGO component (Figure 5)12, 36).