English, John C.

Context.— The accurate identification of different lung adenocarcinoma histologic subtypes is important for determining prognosis but can be challenging because of overlaps in the diagnostic features, leading to considerable interobserver variability. Objective.— To provide an overview of the diagnostic agreement for lung adenocarcinoma subtypes among pathologists and to create a ground truth using the clustering approach for downstream computational applications. Design.— Three sets of lung adenocarcinoma histologic images with different evaluation levels (small patches, areas with relatively uniform histology, and whole slide images) were reviewed by 17 international expert lung pathologists and 1 pathologist in training. Each image was classified into one or several lung adenocarcinoma subtypes. Results.— Among the 4702 patches of the first set, 1742 (37%) had an overall consensus among all pathologists. The overall Fleiss κ score for the agreement of all subtypes was 0.58. Using cluster analysis, pathologists were hierarchically grouped into 2 clusters, with κ scores of 0.588 and 0.563 in clusters 1 and 2, respectively. Similar results were obtained for the second and third sets, with fair-to-moderate agreements. Patches from the first 2 sets that obtained the consensus of the 18 pathologists were retrieved to form consensus patches and were regarded as the ground truth of lung adenocarcinoma subtypes. Conclusions.— Our observations highlight discrepancies among experts when assessing lung adenocarcinoma subtypes. However, a subsequent number of consensus patches could be retrieved from each cluster, which can be used as ground truth for the downstream computational pathology applications, with minimal influence from interobserver variability.

AbstractPleuroparenchymal fibroelastosis (PPFE) is a newly described form of interstitial lung disease that originates in the upper lung zones and typically progresses to involve the entire lung. The disease may be idiopathic but is often associated with other pre‐ or coexisting conditions. Pneumothorax is a common complication and can occur at presentation or at other times during the course of the disease. Pathologically, interstitial fibrosis takes the form of a dense consolidation with some preservation of alveolar septal outlines and demonstrates a distinctly abrupt interface with residual normal lung. Unrecognized cases of PPFE may be incorrectly diagnosed as sarcoidosis, atypical idiopathic pulmonary fibrosis, or other unclassifiable interstitial pneumonias.