Background. The patients with polymyositis (PM) and dermatomyositis (DM) often develop the malignancies in their clinical course. The incidence of cancer is estimated at about 15%. The risk of cancer is the highest within the first year of myositis diagnosis and drops substantially thereafter. The patients with lung cancer diagnosed more than 5 years after the onset of PM or DM are the minority. Methods and Patients. We surveyed the medical records of patients with lung cancer over the period

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... om 1995 to 2011. Results. We found five patients who developed lung cancer more than 5 years after the diagnosis of PM/DM. Three patients were male, and two were female. The median age was 61.2 (±11.7). Histological types were diverse. The clinical stages ranged from IA to IV. Three patients had smoking histories. Four patients suffered from DM, and one suffered from PM. All patients received oral corticosteroid therapy. Two patients also received ciclosporin, and another two received azathioprine. Anti-Jo-1 antibody was positive in one patient. Four patients were complicated with interstitial pneumonia (IP). Conclusion. These lung cancers diagnosed more than 5 years after the onset of PM/DM were probably related to IP or smoking but might not be comorbid with PM/DM.