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 tumor growth patterns. Thin-section CT and pathologic correlation was evaluated in 19 patients with surgically verified small peripheral carcinomas of the lung (<20 mm in size) that had been detected in a screening trial for lung cancer using spiral CT. Four thin-section CT types of nodules were observed: (a) type L1 (4 of 19, 21%), a fairly well-defined nodule with ground-glass attenuation, corresponding to tumor lepidic growth without alveolar collapse; (b) type L2 (4 of 19, 21%), a partly lobulated nodule with a low but inhomogeneous attenuation, corresponding to tumor lepidic growth scattered 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 attenuation peripheral zone, accompanied by convergence of the bronchovascular structures from surrounding lung parenchyma, which corresponded to desmoplastic response in the central zone and to tumor lepidic growth in the peripheral zone; and (d) type H (7 of 19, 37%), a well-defined nodule with a solid homogeneous attenuation, corresponding to tumor hilic growth. Thin-section CT features of small peripheral carcinomas of the lung can be classified into four types, based on the density distribution of the tumor, which reflect the histologic findings.