Small peripheral carcinomas of the lung: thin-section CT and pathologic correlation

The aim of this study was to clarify the thin-section CT features of small peripheral carcinomas of the lung on the basis of pathologic findings of tu mor growth patterns. Thin-section CT and pathologic correlation was evaluat ed in 19 patients with surgically verified small peripheral carcinomas of t he lung (<20 mm in size) that had been detected in a screening trial for lu ng cancer using spiral CT. Four thin-section CT types of nodules were obser ved: (a) type L1 (4 of 19, 21%), a fairly well-defined nodule with ground-g lass attenuation, corresponding to tumor lepidic growth without alveolar co llapse; (b) type L2 (4 of 19, 21%), a partly lobulated nodule with a low bu t inhomogeneous attenuation, corresponding to tumor lepidic growth scattere d foci of alveolar collapse; (c) type L3 (4 of 21%), an ill-defined nodule with an irregularly shaped higher-density central zone in a ground-glass at tenuation peripheral zone, accompanied by convergence of the bronchovascula r structures from surrounding lung parenchyma, which corresponded to desmop lastic response in the central zone and to tumor lepidic growth in the peri pheral zone; and (d) type H (7 of 19, 37%), a well-defined nodule with a so lid homogeneous attenuation, corresponding to tumor hilic growth. Thin-sect ion CT features of small peripheral carcinomas of the lung can be classifie d into four types, based on the density distribution of the tumor, which re flect the histologic findings.