[Relationship between pleural indentation on computed tomography scans and pleural invasion in small peripheral lung cancer of 2 cm in size or less].

Eighty-six cases of small peripheral lung cancer without contact with the chest wall on computed tomography (CT) scans were studied on the presence of radiological pleural indentation and pathological pleural invasion. Twenty-three tumors in 44 cases with pleural indentation were found to reach the pleura histologically, but only one in 42 cases without pleural indentation. There is a high possibility of pleural invasion or contact with the pleura in small lung cancers with pleural indentation. There was no relationship between the presence of pleural indentation and the tumor/chest wall distance on CT scans. Pleural indentations were more frequently seen in small adenocarcinomas of low ground-glass opacity (GGO) ratio or Noguchi's type C. Small lung nodules with pleural indentation had better be removed as early as possible because of the possibility of pleural invasion and pleural dissemination.