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frequency of pathological nodal metastasis is quite distinct based on the presence of GGO component, which is approximately estimated that the patho-logical nodal metastasis is found in 3-5% of part-solid lung cancer (0.50.5), the prognosis is significantly different between the part-solid tumor with GGO and the pure-solid tumor without GGO, and the survival differences were never shown in radiolog-ical invasive NSCLC with GGO component (0.5< CTR<1.0), which was regardless of solid compo-nent size or CTR10, 13, 17). All the more, the prognosis is quite excellent showing more than 90% in 5y overall survival (OS), if tumor has a GGO compo-nent10-13, 15, 23, 24). In contrast, 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 radiologically part-solid lung cancers. Further-more, as shown in our previous study (Figure 2), the prognostic impact of the tumor size is consid-ered to be meaningful only in the pure-solid NSCLC10-13, 15, 23, 24). That is, the survival curves split almost fairly among the different solid component sizes only in radiological pure-solid lung cancer. This 54Figure 2　Clinical T category was compared in the GGO and Solid groups, respectively. The 5y-OS was excellent being 90% or more despite the revised T categories, provided the tumor had a GGO appearance. In contrast, maximum tumor size significantly separated the OS in the Solid arm (p<0.001)12).fact is extremely important when considering future revision of the clinical T staging 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.Proposal for novel clinical T stagingBased on the latest clinical evidences, we are rigorously proposing a proper lung cancer staging for the next clinical T classification. Currently, solid component size is used as a clinical T factor based on the 8th edition of TNM staging system7) (Figure 3). However, several issues are arising regarding the application of the solid component size as a clinical T staging. At first, inconsistency exists between radiological solid component size and pathological invasive size in part-solid lung adenocarcinomas, because the solid area often represents a benign scar or a fibrous scar harboring a stromal invasive component in part-solid tumors25, 26). Furthermore, there are several findings of part-solid tumors in which the solid component size is quite difficult or impossible to measure due to the presence of multiple, complicated or scattered solid areas rather than a single focus8, 9, 27), which has not been abso-lutely determined in the new proposal. In the 8th edition of the T classification, there is no consensus