From basic lesions to a pathological staging of pulmonary fibrosis

Idiopathic pulmonary fibrosis is a severe disease, with unpredictable evolution that frequently leads to respiratory failure and death, despite some progresses made in the field of therapy. Basically, the bad prognosis and failure of therapy are the consequence of the lack of data about the molecular events that have as result the extensive fibrosis. Although the basic lesions were defined many years ago, the pathological classification of pulmonary fibrosis is controversial. In the present work, we analyzed the prognostic impact of basic microscopic lesions on a possible new classification that could be related to the patient outcome. For this purpose, we have investigated 20 cases with idiopathic pulmonary fibrosis and samples of lung parenchyma were obtained by video assisted thoracoscopy. The specimens were processed by usual histological technique and sections were stained with Hematoxylin-Eosin, Masson's trichrome and Gordon-Sweet silver staining. There were evaluated the lung architecture, the chronic inflammatory infiltrate, macrophages and fibrosis. The distribution and severity of each parameter was converted into points and finally graded from I to IV, with corresponding score from 1 to 12. We found four cases with degree II, 12 with degree III, and four with degree IV. Our results support the hypothesis that the evaluation of basic lesions could be the basis for a more objective classification and staging of lung fibrosis and, possibly, a better prognostic method and, eventually, a predictor for the response to targeted therapy.