Case report: dermatomyositis associated with lung cancer with heterogeneous morphology.

Dermatomyositis (DM) complicated with non-small cell lung cancer (NSCLC) is not rare, and could rapidly develop into severe lung cancer [performance-status score (PS) between 2 and 4]. Moreover, tumor has remarkable heterogeneity, and it is not possible to properly target treatments in cases of relapse without knowing pathological diagnosis. We retrospectively analyzed the diagnosis and treatment of a patient with DM complicated with NSCLC, which developed into severe lung cancer with heterogeneity of the tumor during chemotherapy. In this report, we addressed that in patients with severe lung cancer, both the cancer and factors associated with exacerbation should be simultaneously managed to reduce the PS score and avoid unnecessary delay. A second biopsy is important for proper management of the tumor with heterogeneity.