Acute exacerbation, high magnification
Acute exacerbation, high magnification

At higher magnification, aggregates of organizing pneumonia (op) can be seen in the residual alveolar spaces surrounding collapsed alveoli. Fibrosis is present in the alveoli as well (f). These findings are consistent with acute exacerbation of IPF. In some cases diffuse alveolar damage with hyaline membranes can be seen.