Correlation of the solid part on high-resolution computed tomography with pathological scar in small lung adenocarcinomas.

OBJECTIVE To predict the grade of invasion in small (</=3 cm in diameter) lung adenocarcinomas from preoperative high-resolution computed tomography (HRCT), we measured CT numbers of the solid part and compared these with pathological features. METHODS We reviewed 131 cases of lung adenocarcinoma (</=3 cm in diameter) surgically resected between January 1999 and December 2000, which had >10% ground glass opacity (GGO) area on HRCT. The CT numbers of solid parts were measured on HRCT in each tumor. According to our criteria of histopathological grade of stromal invasion, all tumors were classified into four grades: no evidence of stromal invasion (Grade 0), stromal invasion in the area of bronchioloalveolar growth (Grade 1), stromal invasion localized on the periphery of a fibrotic focus (Grade 2), and stromal invasion into the center of a fibrotic focus (Grade 3). RESULTS Nineteen cases that had pure GGOs were excluded. In 112 cases that showed a mixed type of both GGO and solid part, the mean CT number of the overt-invasion group was significantly higher than the no invasion and micro-invasion groups. We adopted -40 as a threshold CT number to determine the degree of invasion. Tumors with values <-40 included no case of overt invasion. CONCLUSIONS Small lung adenocarcinomas with a solid part CT number under -40 in on HRCT usually show no invasion or micro-invasion. Limited surgery may be indicated for such cases because of their good prognosis.