Yoo H, et al. - In this retrospective study of clinical data of 938 patients diagnosed with idiopathic pulmonary fibrosis (IPF) without lung cancer, researchers examined the cumulative incidence, risk factors, and clinical characteristics of lung cancer in IPF. During the follow-up period, lung cancer developed in 135/938 (14.5%) patients. At 1, 3, 5, and 10 years, the cumulative incidence of lung cancer was 1.1%, 8.7%, 15.9%, and 31.1%, respectively. Male gender, current smoking at IPF diagnosis, and a rapid annual decline of 10% or more in forced vital capacity were identified as the risk factors of lung cancer. Mostly elderly men with smoking history developed lung cancer. The most common histologic type was squamous cell carcinoma followed by adenocarcinoma. Lung cancer was frequently located in areas abutting or within fibrosis. Patients with lung cancer had significantly worse survival than patients with IPF alone.