Paraneoplastic polymyositis associated with primary lung cancer: diagnosis with PET-CT

Abstract

0212-6982/$ see front matter © 2010 Elsevier Espana, S.L. and SEMNIM. All rights reserved. A 63-year-old male was studied for cough, dysphagia, fever, pain and functional impotence of both shoulders. He presented an elevation in serum creatinin phosphokinase (42.150 IU/L, normal range: 25-90) and acute phase reactants. A pulmonary nodule was observed on chest radiography, being confirmed by CT in the upper left pulmonary lobe suggestive of malignancy. Non significant millimetric lymph nodes and a right apical pulmonary lesion were observed probably in relation to chronic changes. PET-CT with 18F-FDG was performed showing two nodules in the anterior segment of the upper left lobe (fig. 1) and the posteriorapical segment of the upper right lobe of 2.1 and 1.4 cm, respectively, both of which were hypermetabolic (SUVmax. 2.7 and 2.8) suggestive of malignancy. Likewise, an important diffuse increase in glycidic metabolism was observed in the muscular system (fig. 2) compatible with polymyositis, considering the absence of a history of diabetes and normal glycemia values (103 mg/dL) prior to the injection of 18F-FDG after 12 h of fasting. The left wall of the esophagus showed focal augmentation of glycidic metabolism (SUVmax. 7.2) of 0.8 cm in diameter (fig. 3) compatible with muscular activity without pathological significance, although evaluation was recommended due to the impossibility of ruling out neoplastic disease at this level in view of the clinical manifestations of dysphagia presented by the patient. Fine needle aspiration puncture and prognostic mediastinoscopy were performed with anatomopathological results of pulmonary adenocarcinoma. On evaluation by the Neurology Department by cervical magnetic resonance, electromyogram and blood analysis, the patient was diagnosed with inflammatory myopathy or probable paraneoplastic origin. Upper digestive endoscopy did not show either intraluminal lesion or extrinsic compressions, with the esophageal lesion being labeled as probable paraneoplastic muscular involvement. Initial corticoid treatment was implemented with clinical and analytical improvement, although functional impotence and dysphagia persisted. Chemotherapy was begun on the patient not being a candidate for surgery due to the contralateral pulmonary metastasis. Polymyositis may be of neoplastic origin in up to 20 % of the cases.1 PET-CT with 18F-FDG has shown to be useful in the study of paraneoplastic syndromes to confirm and localize the primary tumor.2 The typical finding is an augmentation of glycidic metabolism in the muscular masses affected by inflammation of the same and usually has a good correlation with the clinical manifestations, also allowing localization of the primary tumor and its extension.3 The case presented here was a pulmonary carcinoma, one of the malignant tumors most frequently related to paraneoplastic polymyositis. PET demonstrated the typical findings of this disease. We believe that PET-CT may be a first choice technique on suspicion of paraneoplastic inflammatory myopathy. Interesting image