Serial high resolution CT in non-specific interstitial pneumonia: prognostic value of the initial pattern
Introduction
The idiopathic interstitial pneumonias can be classified into five main types: usual interstitial pneumonia (UIP), desquamative interstitial pneumonia (DIP), acute interstitial pneumonia (AIP), cryptogenic organizing pneumonia (COP), and non-specific interstitial pneumonia (NSIP).1 The term NSIP was used by Katzenstein and Fioreli2 in 1994 to describe histological appearances which consisted of varying degrees of interstitial inflammation and fibrosis but did not conform to the typical features of UIP, DIP, AIP or COP. In contrast to UIP, the interstitial inflammation in NSIP is temporally uniform.1
Histological appearances in NSIP can be broadly subclassified according to the relative amounts of inflammation and fibrosis into: interstitial inflammation predominant (Group 1), mixed (Group 2), and fibrosis predominant (Group 3).2 Travis et al. showed similar clinical and survival characteristics between mixed and fibrosis predominant groups and therefore proposed subdivision into cellular and fibrotic groups.3 They demonstrated that cases with cellular pattern on histology have a better prognosis than those with a fibrotic pattern. The aim of the current study was to determine how the high resolution (HR) CT pattern in NSIP correlated with histological pattern and whether the CT pattern could reliably predict subsequent disease progression.
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Patients
All open and thoracoscopic lung biopsy diagnoses of NSIP from two institutions over an 8-year period (1993–2000) were identified by a review of computer records. A subset of cases in which serial HRCT had been performed was selected. The histological specimens were reviewed by an expert pulmonary pathologist. Only cases in which the expert pathologist agreed with the initial histological diagnosis of NSIP according to defined criteria (1,3-5) were included in the analysis.
The study group
Histopathological features
There were 4 cases (11%) of NSIP 1 (predominant interstitial inflammation); 13 cases (34%) of NSIP 2 (mixed inflammation and fibrosis); and 21 cases (55%) of NSIP 3 (predominant fibrosis).
PFT findings
In 5 patients, initial and follow-up PFT data were not available. Of the remaining 33, improvement or deterioration in FVC of at least 10% was observed in 19 (58%) and 2 (6%) cases, respectively.
HRCT features
The initial and follow-up HRCT images were considered abnormal by both observers in all 38 patients.
There was
Discussion
NSIP was described in 1994 by Katzenstein and Fiorelli2 in an attempt to prevent the over-diagnosis of UIP. Characterized by varying amounts of interstitial inflammation and fibrosis it is a histological diagnosis of exclusion, in which some features may resemble UIP, DIP, COP, or AIP but are not characteristic of any of these entities. It is clear that the prognosis in NSIP is generally better than in UIP.8, 9, 10 Even in individuals with a fibrosing pattern of NSIP, the 5-year survival of 90%
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