An 82 year-old-woman was referred to our hospital because of infiltrative shadow of the lingula in 201X. She was asymptomatic, so we followed up with imaging observation. After 1 year, the infiltrative shadow had progressed, so we performed bronchoscopy. Glandular epithelium with the mild aberrant type was detected, but did not lead to a definitive diagnosis. There was increased eosinophilic compartmentalization of immune response in the bronchoalveolar lavage, so we started treatment with corticosteroids for chronic eosinophilic pneumonia. However, there was no improvement of the shadow. Subsequent computed tomography-guided lung biopsy revealed evidence of papillary adenocarcinoma.