Lung cancer with MET exon 14 skipping mutation presenting with a crazy-paving appearance

An 88-year-old man was referred due to an abnormality on a chest radiograph performed during routine pre-operative screening. He had a minimal smoking history and was otherwise asymptomatic. Chest radiography (Figure 1A) revealed a ground-glass opacity in the left upper lung field. Chest computed tomography (Figure 1B) showed a 35-mm, ill-defined lesion with a crazy-paving appearance in segment S3a of the left lung, which demonstrated slight interval growth over six months. 18F-FDG PET/CT revealed mild uptake (SUVmax = 2.2), primarily distributed along the pulmonary veins within the lesion (Figure 1C). The patient underwent a left upper lobectomy (Figure 2A). Histopathological analysis revealed papillary proliferation of atypical epithelial cells along thickened alveolar septa. Intra-alveolar hemorrhage, hemosiderin-laden macrophages, and fibrous intimal thickening of pulmonary vessels were also observed (Figures 2B–G). Immunohistochemistry was positive for CK7 and TTF-1, with a PD-L1 tumor proportion score of approximately 10%. Genetic analysis confirmed a MET exon 14 skipping mutation (c.3082 + 1G>A), and the tumor was diagnosed as non-small cell lung cancer (NSCLC), pathological stage IB (pT2aN0M0). The patient remains under observation without adjuvant therapy based on his preference, and no recurrence has been detected during 6 months of follow-up.