Spreading pattern and CT findings of very early-stage peripheral small-cell lung cancer

Chest CT frequently reveals small pulmonary lesions. If there is no associated hilar or mediastinal lymphadenopathy, small-cell lung cancer (SCLC) is considered to be very early-stage. Few studies, however, have described the characteristic CT findings of very early-stage SCLC. Clarifying these findings would reduce diagnostic delay. The purpose of this study was to determine the characteristic CT findings of very earlystage SCLC. Computed tomography images obtained from 547 consecutive patients with lung cancer between 2003 and 2012 at Tokyo Dental College Ichikawa General Hospital were reviewed retrospectively. One hundred of these patients had SCLC and 447 had non-SCLC (NSCLC). These CT images, along with any that had also been obtained prior to the one on which the final diagnosis was based, were reviewed. In 5 of the cases reviewed, specific findings and a characteristic spreading pattern were identified on CT images that might have allowed a diagnosis of SCLC to have been made sooner. The findings included a sub-pleural, small nodule accompanied by daughter nodules spreading longitudinally along the bronchovascular bundle, no air bronchogram or cavitation, and background emphysematous change. These were not identified on CT images of very earlystage NCSLC, however (n = 22). Awareness of the relevance of these findings would help physicians and radiologists arrive at a differential diagnosis of small pulmonary nodules.