Objective  To summarize the clinical features of patients with polymyositis and malignancy.

  Methods  We retrospectively reviewed the clinical records of patients with polymyositis and malignancy hospitalized at Peking Union Medical College Hospital from October 1989 to June 2013.

  Results  Malignancy was identified in 2.4%(10/424)of patients with polymyositis in the hospital during the studied period. The median age of the 10 patients (3 males and 7 females) was 57 years.All patients had significant proximal muscle weakness. Difficulty in head-lifting, bucking, and hoarseness were each observed in one case. Interstitial lung disease, respiratory muscle involvement, and cardiac involvement were observed in 5, 2, and 6 patients, respectively. The most common types of cancer were lymphoma and lung cancer (3 cases each). Other types included esophageal, gastric, renal, and cervical cancers (1 case each). Malignancies in 7 cases were discovered within 1 year before or after polymyositis diagnosis. The initial demonstrations of malignancies included lymphadenectasis, cough and dyspnea, dysphagia, gross hematuria, and postmenopausal vaginal bleeding. Three asymptomatic patients were identified through screening based on positive feces occult blood test or lung mass. Five out of the 9 patients receiving adequate dose of glucocorticoid recovered completely from polymyositis within 1 month, whereas the remaining 4 patients improved but did not fully recover. Of the 4 patients, 3 patients achieved complete recovery after treatment for cancer.

  Conclusions  Malignancy may interfere with the treatment response and prognosis of polymyositis, therefore patients with polymyositis should have a complete screening for the underlying malignancy. Early cancer treatment should be prescribed to better mitigate symptoms and manage conditions in patients with polymyositis and cancer.