Figure 4a. Noguchi type C adenocarcinoma (localized BAC with active fibroblastic proliferation) in a 52-year-old woman. (a) Transaxial thin-section (1-mm collimation) CT scan (lung window) obtained at the level of the left main bronchus shows a 13-mm nodule in the superior segment of the left lower lobe. Note the areas of ground-glass attenuation in the periphery of the nodule (arrow). (b) Low-power photomicrograph (original magnification, x12; H-E stain) of a surgical specimen shows tumor consisting of foci of lepidic growth (spread of neoplastic cells on airspace surface with preservation of underlying lung architecture) (arrows), along with fibrosis and alveolar collapse (arrowheads). At CT, the latter findings appeared as hyperattenuating nodules, whereas the foci of lepidic growth appeared as areas of ground-glass attenuation. The surgical specimens showed no hilar or mediastinal nodal metastasis, but intrapulmonary recurrence was seen at postoperative follow-up.