Interstitial lung abnormality (ILA) and nonspecific interstitial pneumonia (NSIP)

Abstract

This review article aims to address mysteries existing between Interstitial Lung Abnormality (ILA) and Nonspecific Interstitial Pneumonia (NSIP). The concept and definition of ILA are based upon CT scans from multiple large-scale cohort studies, whereas the concept and definition of NSIP originally derived from pathology with evolution to multi-disciplinary diagnosis. NSIP is the diagnosis as Interstitial Lung Disease (ILD) with clinical significance, whereas only a part of subjects with ILA have clinically significant ILD. Eventually, both ILA and NSIP must be understood in the context of chronic fibrosing ILD and progressive ILD, which remains to be further investigated.

Keywords: AIP, acute interstitial pneumonia; ATS/ERS, American Thoracic Society/European Respiratory Society; BIP, bronchiolitis obliterans with interstitial pneumonia; BOOP, bronchiolitis obliterans organizing pneumonia; CT; CTD, connective tissue disease; Connective tissue disease (CTD); DIP, desquamative interstitial pneumonia; GGO, ground-glass opacities; GIP, giant cell interstitial pneumonia; HRCT; HRCT, high-resolution CT; IIP, idiopathic interstitial pneumonia; ILA, interstitial lung abnormality; ILD, interstitial lung disease; Interstitial lung abnormality (ILA); Interstitial lung disease (ILD); LIP, lymphoid interstitial pneumonia; NSIP, nonspecific interstitial pneumonia; Nonspecific interstitial pneumonia (NSIP); Pulmonary fibrosis; RB-ILD, respiratory bronchiolitis-associated interstitial lung disease; UIP, usual interstitial pneumonia; fNSIP, fibrosing nonspecific interstitial pneumonia.

Fig. 1

Idiopathic fibrosing nonspecific interstitial pneumonia in a 40-year-old man. (a, b) Lung window images of CT scans obtained at levels of right interior pulmonary vein (a) and liver dome (b), respectively, show reticular lesions and traction bronchiectasis and bronchiolectasis (arrowheads) along bronchovascular bundles (arrows) and along subpleural lungs (open arrows). (c) Low-power magnification of lung obtained from left lower lobe by video-assisted transthoracic surgery (VATS) demonstrates temporally uniform interstitial fibrosis with minimal architectural distortion.

Fig. 2

Fibrosing nonspecific interstitial pneumonia in a 43-year-old woman with interstitial pneumonia with autoimmune features (IPAF; fluorescent antinuclear antibody [FANA], 1:640). (a, b) Lung window images of CT scans obtained at levels of right interior pulmonary vein (a) and liver dome (b), respectively, show reticular lesions and traction bronchiolectasis (arrowhead in b) in bilateral subpleural lungs. (c) Low-power magnification of lung obtained from right lower lobe by VATS demonstrates mild pleural fibrosis, and airway centered fibrosis containing lymphoid aggregates including some with germinal centers. Although not specific, lymphoid follicles with germinal centers are often associated with connective tissue disease.

Fig. 3

Interstitial lung abnormality combined with lung adenocarcinoma in a 71-year-old man. (a, b) Lung window images of CT scans obtained at levels of right interior pulmonary vein (a) and liver dome (b), respectively, show subpleural reticular lesions mixed with some ground-glass opacity in both lungs. Also note a 26-mm-sized nodule in right lower lobe. Inset in a: high fluorodeoxyglucose uptake within nodule at positron emission tomography indicating malignant nature of nodule. (c) Low-power magnification of lung obtained from a right lower lobectomy demonstrates focal subpleural fibrosis with cystic spaces and anthracosis. Histologically similar images shown by Miller et al⁶⁴ and Hung et al⁶⁵ were classified as UIP.

Fig. 4

Interstitial lung abnormality and mucin-producing lung adenocarcinoma in a 73-year-old man. (a, b) Lung window images of CT scans obtained at levels of suprahepatic inferior vena cava (a) and liver dome (b), respectively, show reticular lesions and traction bronchiolectasis (arrowheads) in both lungs. Also note a 23-mm-sized lung nodule in left lung base. Inset: rather mild fluorodeoxyglucose uptake within nodule at positron emission tomography indicating mucin-producing nature of lung cancer. (c) Low-power magnification of lung obtained from a left lower lobe lobectomy demonstrates focal subpleural fibrosis (arrows) with cystic spaces (open arrows). These histologic findings do not meet pathologic criteria for the diagnosis of UIP or fibrosing NSIP.