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OBJECTIVES The diffusing capacity of the lung for carbon monoxide (DLCO) is an indicator of lung damage. We sought to determine whether DLCO is associated with the aggressiveness of lung adenocarcinoma using histopathological indexes, such as tumour differentiation, scar grade, nuclear atypia and the mitotic index. METHODS Fifty-seven patients with low DLCO (≤80% of predicted) and 466 patients with normal DLCO (>80% of predicted) who underwent R0 resection of lung adenocarcinoma between 2005 and 2012 were retrospectively reviewed. The relationships between the DLCO status and each histopathological index as well as the overall survival were evaluated. RESULTS Low DLCO had significant relationships with moderate/poor differentiation (79% vs 57% [low DLCO vs normal DLCO]), scar grade 3/4 (37% vs 18%), nuclear atypia 3 (65% vs 30%) and the mitotic index 3 (26% vs 8%). After adjusting for the age, sex, forced expiratory volume in 1 s, smoking status and tumour size, a low DLCO still showed a significant correlation with the histopathological indexes. These histopathological indexes were all significant factors for the overall survival on log-rank tests. In a multivariable Cox regression analysis with 13 clinicopathological variables, moderate/poor differentiation and nuclear atypia Grade 3 were significant histopathological factors for the overall survival (hazard ratios: 2.16 and 1.84; 95% confidence intervals: 1.10-4.51 and 1.06-3.21; P = 0.024 and 0.029, respectively). CONCLUSIONS Our findings regarding the relationship between DLCO and the histopathological indexes of lung adenocarcinoma suggest that lung damage may be associated with carcinogenesis and progression.

Objectives The T descriptor of thymic epithelial tumours proposed by the International Association for the Study of Lung Cancer and the International Thymic Malignancy Interest Group as well as the Masaoka-Koga system is defined by the anatomical extent of primary tumours, regardless of their size. However, the prognostic significance of tumour size in thymic epithelial tumours has not been fully elucidated. Methods We evaluated the prognostic significance of tumour size in 154 consecutive patients with thymic epithelial tumours including 124 thymomas, 21 thymic carcinomas and 9 neuroendocrine tumours, who underwent complete resection between 2001 and 2014. Results Among all tumours, the median tumour size was 4.9 cm. The median thymoma, thymic carcinoma and neuroendocrine tumour sizes were 4.8, 5.7 and 5.8, respectively, although the differences were not significant. In survival analysis, the 5- and 10-year overall survival (OS) and recurrence-free survival (RFS) rates for all patients were 91 and 81%, and 80 and 69%, respectively. Under the stratification of tumour size, no trend was observed for OS, whereas RFS showed stepwise deterioration as tumour size increased. For 119 patients with Stage I disease, RFS showed deterioration as tumour size increased. Multivariate analysis revealed that tumour size >4.0 cm was an independent prognostic factor for worsening RFS (P = 0.03). Conclusions Patients with tumours >4.0 cm showed significantly worse outcomes in RFS compared with those with smaller tumours. This relationship was also noted in patients with Stage I disease.