Polymyositis as a Paraneoplastic Syndrome of a Patient With Primary Pulmonary Lymphoepithelioma-like Carcinoma: a Case Report and Literature Review

Abstract Background Pulmonary lymphoepithelima-like carcinoma (LELC) is a rare type of non-small cell lung cancer, which mostly occurred in non-smoking Asian populations. The prognosis of this tumor is better than other lung cancers. Polymyositis, a kind of idiopathic inflammatory myopathies, may negatively affected the prognosis of patients with lung cancer as a paraneoplastic syndrome (PNPS). LELC seldomly accompanied with paraneoplastic syndrome, thus the treatment strategy and prognosis should be discussed.Case presentationWe report a 49-year-old female patient who was hospitlaized for “ symmetric limb weakness and pain for more than 2 months”. Glucocorticoid-based anti-inflammatory therapy had been performed for over 3 weeks before the patient being hospitalized, however, in vain. The result of serum autoimmune antibody showed Anti-nRNP/Sm (+). The serum level of myoglobin, lactate dehydrogenase and creatine kinase elevated significantly. Electromyogram revealed peripheral nerves injury and myogenic damages. Imaging showed a mass in the posterior basal segment of the left lung. Percutaneous transthroacic needle biopsy was performed and the pathological result was LELC. The patient was diagnosed with pulmonary LELC accompanied with polymyositis. Positron emission tomography computed tomography showed only lpsilateral hilar and mediastinal lymph nodes metastasis. Video-assisted thoracoscopic surgery for the left lower lobe resection and systematic mediastinal lymphadenectomy were performed. Postoperative pathological stage was T2N2M0, IIIa(UICC 8th), and the patient received adjuvant chemotherapy and subsequent radiotherapy. The patient was followed up for 5 months with no recurrence of tumor and the limb weakness and pain relieved apparently after the successful comprehensive treatment of her primary tumor.Conclusion PM is associated with lung cancer, ignoring this relationship may lead to missed diagnosis in clinic. Pulmonary LELC is a rare subtype of NSCLC seldomly accompanied with PNPS. Though PNPS negatively affected the prognosis of patients with other lung cancers,surgery based comprehensive treatment of primary tumor can lead to a prospective prognosis in pulmonary LELC patients with PNPS. And successful treatment of pulmonary LELC can also improve symptoms of PNPS.