T1 non-small cell lung cancer: Imaging and histopathologic findings and their prognostic implications

About 5% of T1 non-small cell lung cancers (ie, lung cancers less than 3 cm in diameter), mostly focal nodular bronchioloalveolar carcinomas and carcinoid tumors, demonstrate no uptake at fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and appear to be indolent in growth; consequently, they are associated with long-term patient survival. About 21% of T1 lung cancers show mediastinal nodal metastasis at the time of diagnosis and about 24% show extrathoracic metastasis, mostly brain metastasis, either at the time of diagnosis or at 1-year follow-up. T1 lung cancers with a large ground-glass attenuation component (50% of tumor volume) at thin-section computed tomography (CT) have a good prognosis with less likelihood of mediastinal nodal or extrathoracic metastasis. On the other hand, solid cancer lesions, especially those with a spiculated margin or with bronchovascular bundle thickening in the surrounding lung, more frequently demonstrate local vessel invasion, lymph node metastasis, and extrathoracic metastasis. In these tumors, work-up for extrathoracic metastases (including whole-body FDG PET or brain magnetic resonance imaging and mediastinoscopy for mediastinal nodes) may be needed, even when CT demonstrates no enlarged nodes in the mediastinum.