Solitary Ground-Glass Nodule Mimicking Lung Cancer due to Focal Progression of Usual Interstitial Pneumonia.

Idiopathic pulmonary fibrosis is often associated with lung cancer, but early malignant lesions mixed with fibrous lesions are not always easy to diagnose. A 78-year-old woman was referred to our hospital due to a ground-glass nodule in the left upper lobe detected on chest high resolution computed tomography during follow-up of chronic idiopathic interstitial pneumonia. Pathological examination of the resected specimen revealed that the ground-glass nodule was locally progressed usual interstitial pneumonia (UIP). It should be noted that focal progression of UIP may occur and present with ground-glass nodule mimicking lung cancer, even if lesions in other areas remain unchanged. Moreover, in such cases, recognition of nodular lesions by the gross findings on the pleural surface and palpation during surgical resection are difficult and require precise marking.