Polymyositis as a paraneoplastic syndrome in cytotoxic molecule-positive and Epstein-Barr virus-associated peripheral T-cell lymphoma, not otherwise specified.

We encountered a rare case of cytotoxic molecule-positive and Epstein-Barr virus (EBV)-associated peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), which was clinically preceded by polymyositis. A 50-year-old woman with a 4-year history of steroid-refractory polymyositis developed ulcerative skin swelling on her left arm. A diagnosis of cytotoxic molecule (TIA-1)-positive and EBV-associated PTCL-NOS was made on the basis of immunohistochemical and molecular examinations of the biopsied brachial muscle. Combination chemotherapies were ineffective, with a fatal outcome. Reassessment of the biopsy specimens of the muscle taken at the age of 46 years showed that the PTCL was already present, indicating that the polymyositis was likely a paraneoplastic manifestation.