Pulmonary Pathology Online
Pathology of Non-Specific Interstitial Pneumonia (NSIP)
Nonspecific interstitial pneumonia (NSIP) has been proposed as a histologic subtype of idiopathic interstitial pneumonia with lung biopsy findings that are inconsistent with those of other idiopathic interstitial pneumonias.
NSIP has a broad spectrum of histologic findings and a variable prognosis.
This is the second commonest pattern of the lung injury seen in idiopathic pulmonary fibrosis (Cryptogenic fibrosing alveolitis).
Histologically, the most important feature is the diffuse and temporally uniform pattern of lung injury with variable degrees of inflammation and fibrosis.
1. Predominantly inflammatory ;
2. Mixed inflammatory and fibrotic ;
3. Predominantly fibrotic.
The predominantly inflammatory cases may resemble extrinsic allergic alveolitis , and the mixed inflammatory and fibrotic cases may be confused with Usual interstitial pneumonia.
Occasional fibroblast foci are seen in some cases and areas of Bronchiolitis obliterans organising pneumonia (BOOP) are present in a number of cases.
It is important to recognize NSIP as a distinct pattern of lung injury, and to differentiate it from usual interstitial pneumonitis (UIP) since the progress of NSIP cases is much better than those of UIP.
It is differentiated from usual interstitial pneumonitis by the temporal uniformity of the lesions, a prominent inflammatory interstitial infiltration, and the absence of honeycombing.
A more recent study has suggested that NSIP should be divided into cellular and fibrosing patterns, as these were shown to have different clinical characteristic and prognosis.
Patients with NSIP, cellular pattern had a better survival than those with NSIP, fibrosing pattern.
It should not be considered a specific disease, however, because it may have varying etiologies including :
- underlying connective tissue diseases.
The histological findings of NSIP may be a manifestation of collagen vascular disease in a number of patients.
NSIP seems to be the major histopathologic pattern in patients with pulmonary fibrosis associated with scleroderma .
- organic dust or other exposures ;
- drug reaction or unusual examples of extrinsic allergic alveolitis particularly if the changes show centri-acinar accentuation ;
- prior acute lung injury ;
- less often, it may reflect a nonrepresentative biopsy of another process (may be poorly sampled BOOP or poorly sampled UIP).
Nonspecific interstitial pneumonia must be separated from the three main forms of idiopathic interstitial pneumonia because prognosis is rather good, since a majority of patients improve when treated with corticosteroids or with an association of corticosteroids and immunosuppressive drugs.
According to some authors idiopathic NSIP may be the first manifestation of a systemic autoimmune disease.
Idiopathic Pulmonary Fibrosis ; Respiratory bronchiolitis-interstitial lung disease (RBILD); Usual Interstitial Pneumonia (UIP) ; Desquamative interstitial pneumonia (DIP) ; Acute interstitial pneumonia (AIP)/organizing diffuse alveolar damage DAD); Lymphocytic Interstitial Pneumonia/Follicular Bronchiolitis.
Idiopathic nonspecific interstitial pneumonia: prognostic significance of cellular and fibrosing patterns: survival comparison with usual interstitial pneumonia and desquamative interstitial pneumonia.
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