Benjamin Felson lecture. Chronic interstitial lung disease of unknown cause: a new classification based on...

Chronic interstitial lung disease of unknown cause is usually classified on the basis of descriptive histology. In this lecture, a recently published series of 910 cases of chronic interstitial lung disease is used to show that these descriptive terms can be reorganized into a classification that is based on inflammatory and neoplastic processes. The proposed classification includes three major diagnostic categories, two of which are based on the chronic inflammatory response and a third that results from infiltration of the interstitial space by neoplastic cells of either a benign, borderline, or frankly malignant nature. An argument is presented that the steps involved in the development of the endstage of chronic interstitial lung disease are similar in all three groups. The advantage of this new classification is that it shifts the emphasis from descriptive terminology to pathogenesis, which provides a more critical basis for investigation of the causes of these diseases.