MPO and idiopathic interstitial pneumonia: However, in comparison with the pattern of IPF/UIP, differences in histopathological images were evident; in MPO‐ANCA/UIP, the interstitium demonstrates mononuclear cell infiltration, particularly an increase in plasma cells; hyperplasia of lymphoid follicles with germinal centers, cellular bronchiolitis, and cyst formation are also prominent [9].