Evaluation of solid portions in non-small cell lung cancer-the solid part is not always measurable for clinical T factor.

BACKGROUND Solid component size on thin-section computed tomography is used for T-staging according to the eighth edition of the Tumor Node Metastasis classification of lung cancer. However, the feasibility of using the solid component to measure clinical T-factor remains controversial. METHODS We evaluated the feasibility of measuring the solid component in 859 tumours, which were suspected cases of primary lung cancers, requiring surgical resection regardless of the procedure or clinical stage. After excluding 126 pure ground-glass opacity tumours and 450 solid tumours, 283 part-solid tumours were analysed to determine the frequency of cases where the measurement of the solid portion was difficult along with the associated cause. Pathological invasiveness was also evaluated. RESULTS The solid portion of 10 lesions in 283 part-solid nodules was difficult to measure due to an underlying lung disease (emphysema and pneumonitis). The solid portion of 62 lesions (21.9%) without emphysema and pneumonitis was difficult to measure due to imaging features of the tumours. Among the 62 patients, five had no malignancy and one with a tumour size of 33 mm had nodal metastasis. There were 56 lesions with a tumour size of ≤30 mm, wherein nodal metastases, vascular and/or lymphatic invasions were not observed. CONCLUSION For one-fifth of the part-solid tumours, measurement of the solid component was difficult. Moreover, these lesions had low invasiveness, especially in T1. The measurement of the solid portion and the classification of T1 in 1-cm increments may be complex.