Abstract: Objective To investigate the clinical features of dermatomyositis and polymyositis associated with malignancy. Methods A retrospective study was performed of 313 patients with a diagnosis of dermatomyositis and polymyositis admitted to the First Affiliated Hospital of Sun Yat-sen University over a period of 15 years. The clinical characteristics and risk factors of cases associated with malignancy were analyzed. Results Among these 313 patients with dermatomyositis and polymyositis, the incidence of malignancy was 14.38%(45/313).Of the 45 patients with malignancy, 69%(31/45)cancers were diagnosed at the same time as dermatomyositis and polymyositis, and the most common malignancies were nasopharyngeal carcinoma, lung cancer, and breast cancer. Statistical analyses revealed that the high risk factors of concomitant malignancy included an onset in older age(>40 years)(P=0.0047, OR=0.186)and a shorter disease history(<1 year)(P=0.0033, OR=3.884). Conclusions These results provide evidence that dermatomyositis and polyrnyositis are frequently associated with a wide variety of cancers, particularly carcinoma of nasopharynx, lung, and breast. Patients over 40 years of age or with a disease history of less than 1 year should be screened for possible associated malignancy.

Key words: Dermatomyositis, Nasopharyngeal neoplasms, Lung neoplasms, Breast neoplasms;Syndromes, paraneoplastic