Polymyositis as a paraneoplastic syndrome of a patient with primary pulmonary lymphoepithelioma-like carcinoma: a case report and literature review.

BACKGROUND: Pulmonary lymphoepithelioma-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 affect the prognosis of patients with lung cancer as a paraneoplastic syndrome (PNPS). LELC is seldomly accompanied by PNPS, thus the treatment strategy and prognosis should be discussed.

CASE PRESENTATION: We report a 49-year-old female patient who was hospitalized 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 was 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. An electromyogram revealed peripheral nerves injury and myogenic damages. Imaging showed a mass in the posterior basal segment of the left lung. A percutaneous transthoracic needle biopsy was performed and the pathological result was LELC. The patient was diagnosed with pulmonary LELC accompanied by polymyositis. Positron emission tomography-computed tomography (PET-CT) showed only ipsilateral hilar and mediastinal lymph nodes metastasis. Video-assisted thoracoscopic left lower lobectomy and systematic mediastinal lymphadenectomy were performed. The 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 were relieved apparently after the successful comprehensive treatment of her primary tumor.

CONCLUSION: Pulmonary LELC is a rare subtype of non-small cell lung cancer seldomly accompanied by PNPS. Though polymyositis is associated with lung cancer, it is easy to ignore this relationship when a patient is diagnosed with LELC in the clinic. 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.