Characteristics of non-small-cell lung cancer with interstitial pneumonia: variation in cancer location, histopathology, and frequency of postoperative acute exacerbations in interstitial pneumonia

Background Non-small-cell lung cancer (NSCLC) has been reported to develop in patients with interstitial pneumonia (IP); however, clinical, radiological, and pathological features remain to be elucidated. Methods We retrieved the records of 120 consecutive NSCLC patients associated with IP who underwent surgery at Toranomon Hospital between June 2011 and May 2017. We classified the patients into three groups according to NSCLC location using high-resolution computed tomography: group A, within a fibrotic shadow and/or at the interface of a fibrotic shadow and normal lung; group B, within emphysematous tissue and/or at the interface of emphysematous tissue and normal lung; and group C, within normal lung. In 64 patients, programmed death ligand-1 (PD-L1) status was assessed with immunohistostaining. Results Most of the patients (89; 70%) were classified as group A. This group tended to have squamous cell carcinoma with the usual interstitial pneumonia (UIP). These cancers were located mainly in the lower lobes and seven of the eight postoperative acute exacerbations (pAE) of IP developed in this group. NSCLC in the group B were mainly squamous cell carcinomas located in the upper lobes. No patient with PD-L1 negative was classified into group B. None of the patients in group C showed UIP. and most of the cancers were adenocarcinoma. The frequency of epidermal growth factor receptor mutation-positive NSCLC was the highest in this group. Conclusions The three groups each showed characteristic features in terms of tumor location, histopathology, PD-L1 expression, and frequency of pAEof IP.