Abstract
Dermatomyositis (DM) is associated with an increased risk of lung cancer. Misdiagnosed the squamous carcinoma of lung with DM is illustrated by the case who was a 73-year-old male and underwent successful surgical lobectomy presented here. The lack of examination of chest computed tomography (CT) is also emphasized. DM in an adult is a rare clinical entity. To facilitate the preoperative diagnosis and avoid the misdiagnosis of this disease, more etiological factors need to be considered.