ABSTRACT
Usual interstitial pneumonia (UIP) is a distinctive pathological pattern that is seen in the lungs of patients with diffuse parenchymal lung disease (DPLD) (9,19,43,44). It is the most common and most important of the group of DPLDs regarded as idiopathic interstitial pneumonias (IIPs) (Table 1) (43,44). The lung injury in UIP is often distributed along the subpleural and paraseptal regions and is characterized by patchy, temporally heterogeneous fibrosis with scattered fibroblastic foci at the edges of dense fibrotic scars that cause remodeling of the lung architecture and microscopic honeycombing (Table 1) (9,19,43,44). The UIP pattern can be seen in patients with collagen vascular disease, chronic hypersensitivity pneumonitis, pneumoconiosis (particularly asbestosis), drug toxicity, and with no apparent cause. In the latter setting, the clinical-radiological-pathological terms idiopathic pulmonary fibrosis (IPF) or cryptogenic fibrosing alveolitis (CFA) are appropriate (23,44).
