Fig. 2

Selected criteria set images taken from the project website illustrative of problems and potential solutions in diagnoses of chronic fibrotic ILD [13]. a Fibrosis criteria set image 5, also used as Inflammation criterion set image 4, b Fibrosis criteria set image 25, c Fibrosis criteria set image 2, d granuloma criteria image 1. Figure 2a shows fibrosis which is focally severe predominantly around the airways in the center of the image although there is a connection to the adjacent interlobular septa. Figure 2b shows mildly cellular fibrosis without dense (“collagen”) fibrosis. The fibrosis seems to merge continuously into the non-fibrotic region without an easily drawn boundary. There is marked bronchiolectasis (the airway in the right middle is massively enlarged relative to the adjacent artery) while there is minimal fibrosis around that airway itself. This pattern of fibrosis is not clearly defined in established criteria and generates conflicting interpretation in the diagnostic categories. See text for additional discussion