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Nonspecific Interstitial Pneumonia

Definition

  • Idiopathic interstitial lung injury demonstrating temporal uniformity and lacking diagnostic features of other diseases

Alternate/Historical Names

  • NSIP

Diagnostic Criteria

  • Clinical
    • Insidious onset of dyspnea, cough, fatigue
    • Mean age 40-50, may be seen in children
    • Pulmonary function tests: restrictive with decreased diffusing capacity
      • Generally less severe than UIP
    • Overall 80=90% 5 year survival
      • Responds to steroids
  • High resolution computed tomography (HRCT)
    • Predominantly ground glass opacities
    • Changes bilateral, predominantly basal and peripheral
    • Reticular, linear patterns may also be seen in 50%
    • Focal honeycombing only seen in occasional cases
  • Histopathologic features
    • Changes in a given case are temporally uniform
    • Interstitial inflammation ranges from mild to moderate
      • Lymphoid follicles frequently present
    • Type II pneumocyte hyperplasia
    • Scant to dense interstitial fibrosis
      • Generally preserves lung architecture
        • EVG may be useful
        • Honeycomb change is seen only in occasional cases and is not predominant
      • Air spaces may be enlarged
      • Traction bronchiolitis may be seen
        • Bronchiole surrounded by fibrosis and larger than adjacent muscular artery
    • Has been separated into two types
      • Cellular type
        • Changes are predominantly cellular, with scant fibrosis
        • Better prognosis
      • Fibrotic type
        • Changes are predominantly fibrotic, with less cellularity
    • NSIP is a diagnosis of exclusion
      • The following features should not be seen
        • Granulomas or giant cells
        • Bronchiolocentric distribution
        • Acute lung injury pattern / hyaline membranes
        • More than rare eosinophils
        • Evidence of infection
      • Some features of other types of interstitial lung disease may be seen to a limited extent, but do not predominate
    • Discordant features may be seen (UIP on one biopsy, NSIP on another)
      • Behaves as UIP
      • Multiple biopsies are recommended, if possible
  • The following must be ruled out in every case
    • Collagen vascular disease
    • Drug reaction
    • Chronic hypersensitivity pneumonitis
      • Giant cells and or granulomas
      • Predominantly bronchiolocentric distribution
    • Immunodeficiency related changes
    • Infection
      • Acid fast and fungal stain should be performed in every case
    • Slowly resolving acute interstitial pneumonia
    • Sampling error (see Discordant above)

Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 11/20/10

Differential Diagnosis

NSIP is a diagnosis of exclusion

Infection must be ruled out in every case

Usual Interstitial Pneumonia Nonspecific Interstitial Pneumonia
Temporal and spatial heterogeneity Temporal and spatial uniformity
Honeycomb change prominent Honeycomb change rare
Scant interstitial inflammation Prominent interstitial inflammation
Prominent fibroblastic foci Fibroblastic foci few, focal

Classification / Lists

Idiopathic Interstitial Lung Diseases

Other Diffuse Parenchymal Lung Diseases

 

Bibliography

  • Travis WD, Colby TV, Koss MN, Rosado-de-Christenson ML, Müller NL, King TE Jr.  Non-neoplastic Disorders of the Lower Respiratory Tract, AFIP Atlas of Nontumor Pathology, First Series, Fascicle 2, 2002.
  • American Thoracic Society; European Respiratory Society. ATS/ERS International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001. Am J Respir Crit Care Med. 2002 Jan 15;165(2):277-304
  • Visscher DW, Myers JL. Histologic spectrum of idiopathic interstitial pneumonias. Proc Am Thorac Soc. 2006 Jun;3(4):322-9.
  • Travis WD, Hunninghake G, King TE Jr, Lynch DA, Colby TV, Galvin JR, Brown KK, Chung MP, Cordier JF, du Bois RM, Flaherty KR, Franks TJ, Hansell DM, Hartman TE, Kazerooni EA, Kim DS, Kitaichi M, Koyama T, Martinez FJ, Nagai S, Midthun DE, Müller NL, Nicholson AG, Raghu G, Selman M, Wells A. Idiopathic nonspecific interstitial pneumonia: report of an American Thoracic Society project. Am J Respir Crit Care Med. 2008 Jun 15;177(12):1338-47.
  • Travis WD, Matsui K, Moss J, Ferrans VJ. Idiopathic nonspecific interstitial pneumonia: prognostic significance of cellular and fibrosing patterns: survival comparison with usual interstitial pneumonia and desquamative interstitial pneumonia. Am J Surg Pathol. 2000 Jan;24(1):19-33
  • Monaghan H, Wells AU, Colby TV, du Bois RM, Hansell DM, Nicholson AG. Prognostic implications of histologic patterns in multiple surgical lung biopsies from patients with idiopathic interstitial pneumonias. Chest. 2004 Feb;125(2):522-6.
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