摘要Welder's siderosis or pneumoconiosis siderotica is an occupational lung disease which is usually seen after chronic exposure to iron dust,especially in welders.It was first described by Doig and McLaughlin1 in 1936 and occurs in about 7％ of arc welders.Despite striking radiological and histopathological features, it has traditionally been classified as a “benign pneumoconiosis” because of the absence of associated symptoms,functional impairment or pulmonary fibrosis in general.1,2 Although several authors have reported evidence of fibrosis in the lungs of welders,3,4 siderosis with local massive fibrosis described from pathology or occupying lesion on chest CT scans is very rare.5 Here we present a case of Welder's siderosis with local massive fibrosis mimicking lung cancer.