SLB as a Tool for a Marker of Prognosis and the Significance of Fibroblast Foci
In addition of the diagnosis of ILD, SLB can be used also as source of a biomarker for the prognosis in IPF patients. The number of fibroblast foci (FF) i.e. active centers of fibrogenesis consisting of myofibroblasts, fibroblasts and extracellular matrix (ECM) proteins and lined by regenerative hyperplastic or metaplastic alveolar epithelium, has been shown to correlate with patient survival in several studies, but not in all (Table 4). The detailed information of the studies focusing on the number of fibroblast foci is presented in the Table 4.
Despite this quite convincing evidence, the counting of FF in biopsies has not yet become a common routine clinical practice. This might be attributable to the fact that the number of FF has been evaluated with variable methods in the different studies. At present FF has proved to be the only reproducible histological factor that correlates with the prognosis in IPF. There are very few studies, which have evaluated the value of immunohistochemical markers from SLB specimens on survival, since during the past decade most studies focusing on biomarkers have been conducted by using serum or BAL samples. Nearly two decades ago it was reported that a high expression level of the ECM protein, tenascin-C as detected by immunohistochemistry in SLB samples, correlated with shortened survival in patients with UIP.