Figure 4b. Concurrent atypical adenomatous hyperplasia and adenocarcinoma in a 71-year-old woman. (a) Thin-section CT image at the level of the carina shows an 18-mm-diameter mixed nodular ground-glass opacity with a solid component in the upper lobe of the right lung and a 10-mm pure nodular ground-glass opacity in the lower lobe of the left lung. (b) Photomicrograph of a resected specimen (original magnification, x40; hematoxylin-eosin stain) from a superior segment of the lower lobe of the left lung shows atypical epithelial cell proliferation along thickened alveolar septa, findings suggestive of atypical adenomatous hyperplasia. (c) Photomicrograph of a histologic slice (original magnification, x40; hematoxylin-eosin stain) from the right upper lobectomy specimen shows adenocarcinoma, with carcinoma of the bronchioloalveolar subtype at the periphery of the lesion.