Figure 13a.

ALK inhibitor–related pneumonitis in a 55-year-old woman with ALK-positive stage IV adenocarcinoma of the lung. The patient experienced disease progression while taking a first-generation ALK inhibitor (crizotinib) and was then treated with a second-generation ALK inhibitor (ceritinib). She presented with an increasing dry cough and dyspnea at 7 months of ceritinib therapy. (a, b) Axial (a) and coronal (b) CT images show biapical consolidation and GGOs in both upper lobes (arrows) in a striking peripheral distribution, indicative of a COP pattern. (c, d) Photomicrographs from transbronchial lung biopsy specimen show organizing interstitial pneumonia characterized by alveolar interstitial widening by lymphocytic infiltrates, increased extracellular matrix material, reactive pneumocyte hyperplasia, scattered eosinophils (arrow in d), and numerous airspace foamy macrophages. There was no evidence of tumor in the biopsy specimen. (Hematoxylin-eosin stain; original magnification, ×200 in c, ×400 in d.)