High-resolution CT analysis of small peripheral lung adenocarcinomas revealed on screening helical CT

OBJECTIVE. The purpose of this study was to determine the correlation betwe en high-resolution CT morphologic features of small peripheral lung adenoca rcinomas and tumor growth patterns. MATERIALS AND METHODS. We examined high-resolution CT morphologic features of 59 small, surgically resected peripheral lung adenocarcinomas (diameter, 6-20 mm) that were detected on screening for lung cancer using low-dose he lical CT. Among these adenocarcinomas, 14 (24%) were visible and 45 (76%) w ere invisible on conventional chest radiography. The correlation between hi gh-resolution CT morphologic features and tumor growth patterns was analyze d. RESULTS. Sixteen (94%) of 17 type A (Noguchi's classification) adenocarcino mas appeared as nodules of pure ground-glass attenuation (high-resolution C T type I). Ten (71%) of 14 type B tumors appeared as heterogeneous, low-att enuation nodules (type II). Seven (29%) of 24 type C tumors appeared as nod ules with ground-glass attenuation in the periphery and a high-density cent ral zone (type III), and 12 (50%) of 24 type C tumors appeared as homogeneo us nodules with soft-tissue density (type IV). Among tumors with a replacem ent growth pattern, the size and CT values of type C tumors were larger tha n those of type A or type B tumors (p < 0.05), whereas the percentage of gr ound-glass attenuation and retained air space in type C tumors was smaller than those in type A or type B tumors (p < 0.01). All (100%) four type D tu mors appeared to be homogeneous nodules with soft-tissue density (type IV). CONCLUSION. Small peripheral lung adenocarcinomas shown on CT exhibit four high-resolution CT patterns that corresponded to the histopathologic findin gs of different tumor growth patterns.