Histopathology
-
The separation of fibrotic non-specific interstitial pneumonia (FNSIP) and usual interstitial pneumonia (UIP) is important for patient treatment and prognosis, but is sometimes a difficult diagnostic problem. Most authors believe that fibroblast foci are rare in NSIP, and that the finding of multiple fibroblast foci suggests a diagnosis of UIP. Similarly, architectural distortion is viewed as favouring a diagnosis of UIP. This study aims to assess these criteria for their diagnostic utility. ⋯ Otherwise typical FNSIP cases can show architectural distortion caused by confluence or marked expansion of fibrotic alveolar walls. These areas tend to be associated with fibroblast foci. These findings do not imply a poor prognosis, and should not be confused with UIP.