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(Figure 1). When the tumor is surrounded by a GGO component, it is called as part-solid tumor with a GGO. By contrast, pure-solid tumor is recog-nized as a tumor without any GGO component12, 16, 21) (Figure 1). And it is well known that the ratio of consolidation part to the maximum tumor size well reflects the tumor aggressiveness in early-stage lung cancer1). When we defied a consolidation to tumor ratio (CTR), which indicates the ratio of maximum consolidation diameter to the maximum tumor diameter, tumor size less than 2cm and CTR less than 0.25 was defined as a radiologically non-in-vasive lung cancer to predict pathological non-in-vasiveness based on the result of JCOG0201 trial1). Furthermore, the 5-year survival outcome was significantly different when the cutoff point of CTR was selected as 0.5 (CTR≤0.5, radiological non-in-vasive; 96.7%, CTR>0.5, radiological invasive; 88.9%, p<0.001)1, 22). However, even in the radiological invasive lung cancer with a CTR more than 0.5, recent study shows that the presence of a GGO component has a strong impact on the favorable prognosis of lung cancer10, 13, 17). irrelevant to the survival outcome of NSCLC if the tumors show a GGO component10-17). On the other hand, radiologically determined pure-solid lung cancers without a GGO component exhibit more malignant behavior and show several histologic types that have a poorer prognosis than do radio-logically part-solid lung cancers. Thus, the prog-nostic impact of the solid tumor size is considered to be meaningful only in the pure-solid NSCLC10-15). This fact is extremely important when considering future revision of the clinical T staging and the proper operative strategies of lung cancer, provided that the clinicopathologic and oncologic outcomes are disparate between part-solid and pure-solid tumors on the basis of a GGO presence. In this report, we would like to demonstrate the latest clinical evidence regarding the small-sized lung cancer, and to discuss the appropriate operative modes based on these clinical evidences. Latest clinical evidence of small-sized lung cancerTo date, there are numerous studies to evaluate the radiological and pathological correlation of early-stage NSCLC in Japan18-20). Based on the find-ings of thin-section CT scan, small-sized lung cancer is radiologically comprised of 2 parts, which is consolidation part and ground-glass opacity compo-nent1). Ground-glass opacity, or GGO is defined as an area of a slight, homogenous increase in density that do not obscure the underlying vascular marking Figure 1　Definition of the consolidation to tumor ratio, and the typical findings of part-solid tumor and pure-solid tumor based on thin-section computed tomography1).Until now, we focused on the clinicopathological and prognostic importance of a GGO component from several aspects. In general, we have reported that the lung cancer with a GGO component showed less invasive feature compared to the radiological pure-solid tumor. For instance, among patients with clinical-stage IA disease with a radio-logical invasive appearance (i.e., CTR>0.5), the 53