Fibroblastic foci (FF), distinct aggregates of fibroblasts, are one of the pathologic characteristics of usual interstitial pneumonia (UIP). Because a variety of profibrotic agents have been found in FF and most cells in FF are myofibroblasts, FF are thought to represent sites of ongoing lung injury that may progress to dense fibrosis. Recently, there has been increasing interest in the prognostic significance of FF in UIP. Indeed, several studies- have demonstrated the clinical importance of FF as a prognostic parameter in UIP. In idiopathic pulmonary fibrosis (IPF), poor prognosis was shown to be related to greater degrees of FF.’ In those studies, to evaluate the degree of FF, several pathologic scoring systems, such as the Brompton, the Denver,” and the Michigan FF scoring methods, were employed. Briefly, two or more specialists in pulmonary pathology reviewed specimens obtained by surgical lung biopsy and semiquantitatively scored the degrees of FF on several scales. These scoring methods have at least two disadvantages. Link
First, the assessment is somewhat subjective, and not actually quantitative, because interobserver variation is not small when evaluated with the use of unweighted к coefficient of agreement.’ Second, in the practical setting, it is not easy to consult two or more specialists in pulmonary pathology just for quantifying the degree of FF. Indeed, although Flaherty et al showed a positive association among these three scoring methods, the association ratios were relatively low (< 0.56) and some discrepancies were noted in certain clinical parameters, such as predicting survival. Thus, the evaluation of FF degrees may not be identical when different scoring systems are employed. Accordingly, Flaherty et al emphasized the need for further studies to define the optimal way to score the degree of FF. Even in the practical setting, there is a need for a more objective and simple scoring method to assess the degree of FF, which would enable us to easily score FF even without consulting a panel of specialists in pulmonary pathology, and to directly compare our scores with published data and/or the data of others.
The present study was conducted to develop a more objective and quantitative scoring method to accurately assess the degree of FF in UIP. With a charge-coupled device (CCD) camera, we captured the images of specimens of patients with IPF/UIP and collagen vascular disease (CVD)-associated UIP (CVD-UIP), and measured the percentage of FF area (%FF) in the target image areas using image analysis software. Using our quantitative scoring method, we were able to readily and accurately assess the degree of FF. Further, we found that our quantitative FF score was an independent prognostic factor of the survival of patients with UIP. These results suggest that our quantitative FF scoring method, which is easily performed, can provide a more objective and quantitative assessment of the degree of FF.