We report a case, cytologically diagnosed, of broncho-alveolar cancer associated with localised interstitial pulmonary fibrosis. This association of fibrosis with bronchiolo-alveolar cancer is classical and a pathogenic affiliation has been deduced by the majority of authors. We review the pathogenesis in relation to recent datas concerning the activation of successive oncogenes: the first stage of carcinogenesis may correspond to the activation of an oncogene coding for a fibroblastic growth factor leading to fibrosis.